IF ( exch2_pi(1,2,n1).eq.1 ) THEN

         IF ( exch2_pi(2,2,n1).eq.-1 ) THEN

       exch2_pi(1,1,12)=1

       exch2_pi(2,1,12)=0

       exch2_pi(1,2,12)=1

       exch2_pi(2,2,12)=0

       exch2_pi(1,3,12)=0

       exch2_pi(2,3,12)=1

       exch2_pi(1,4,12)=1

       exch2_pi(2,4,12)=0

       exch2_pi(1,1,2)=0

       exch2_pi(2,1,2)=-1

       exch2_pi(1,2,2)=0

       exch2_pi(2,2,2)=-1

       exch2_pi(1,3,2)=1

       exch2_pi(2,3,2)=0

       exch2_pi(1,4,2)=1

       exch2_pi(2,4,2)=0

       exch2_pi(1,5,2)=0

       exch2_pi(2,5,2)=1

       exch2_pi(1,1,3)=1

       exch2_pi(2,1,3)=0

       exch2_pi(1,2,3)=0

       exch2_pi(2,2,3)=-1

       exch2_pi(1,3,3)=0

       exch2_pi(2,3,3)=-1

       exch2_pi(1,4,3)=0

       exch2_pi(2,4,3)=1

       exch2_pi(1,5,3)=1

       exch2_pi(2,5,3)=0

       exch2_pi(1,1,4)=1

       exch2_pi(2,1,4)=0

       exch2_pi(1,2,4)=1

       exch2_pi(2,2,4)=0

       exch2_pi(1,3,4)=0

       exch2_pi(2,3,4)=1

       exch2_pi(1,4,4)=1

       exch2_pi(2,4,4)=0

       exch2_pi(1,1,5)=1

       exch2_pi(2,1,5)=0

       exch2_pi(1,2,5)=1

       exch2_pi(2,2,5)=0

       exch2_pi(1,1,1)=1

       exch2_pi(2,1,1)=0

       exch2_pi(1,3,5)=1

       exch2_pi(2,3,5)=0

       exch2_pi(1,4,5)=0

       exch2_pi(2,4,5)=1

       exch2_pi(1,1,6)=0

       exch2_pi(2,1,6)=-1

       exch2_pi(1,2,6)=0

       exch2_pi(2,2,6)=-1

       exch2_pi(1,3,6)=1

       exch2_pi(2,3,6)=0

       exch2_pi(1,4,6)=1

       exch2_pi(2,4,6)=0

       exch2_pi(1,5,6)=0

       exch2_pi(2,5,6)=1

       exch2_pi(1,2,1)=1

       exch2_pi(1,1,7)=1

       exch2_pi(2,1,7)=0

       exch2_pi(2,2,1)=0

       exch2_pi(1,2,7)=0

       exch2_pi(2,2,7)=-1

       exch2_pi(1,3,7)=0

       exch2_pi(2,3,7)=-1

       exch2_pi(1,4,7)=0

       exch2_pi(2,4,7)=1

       exch2_pi(1,5,7)=1

       exch2_pi(2,5,7)=0

       exch2_pi(1,1,8)=1

       exch2_pi(2,1,8)=0

       exch2_pi(1,2,8)=1

       exch2_pi(2,2,8)=0

       exch2_pi(1,3,8)=0

       exch2_pi(2,3,8)=1

       exch2_pi(1,4,8)=1

       exch2_pi(2,4,8)=0

       exch2_pi(1,3,1)=1

       exch2_pi(2,3,1)=0

       exch2_pi(1,1,9)=1

       exch2_pi(2,1,9)=0

       exch2_pi(1,2,9)=1

       exch2_pi(2,2,9)=0

       exch2_pi(1,3,9)=1

       exch2_pi(2,3,9)=0

       exch2_pi(1,4,9)=0

       exch2_pi(2,4,9)=1

       exch2_pi(1,1,10)=0

       exch2_pi(2,1,10)=-1

       exch2_pi(1,2,10)=0

       exch2_pi(2,2,10)=-1

       exch2_pi(1,3,10)=1

       exch2_pi(2,3,10)=0

       exch2_pi(1,4,1)=0

       exch2_pi(1,4,10)=1

       exch2_pi(2,4,10)=0

       exch2_pi(2,4,1)=1

       exch2_pi(1,5,10)=0

       exch2_pi(2,5,10)=1

       exch2_pi(1,1,11)=1

       exch2_pi(2,1,11)=0

       exch2_pi(1,2,11)=0

       exch2_pi(2,2,11)=-1

       exch2_pi(1,3,11)=0

       exch2_pi(2,3,11)=-1

       exch2_pi(1,4,11)=0

       exch2_pi(2,4,11)=1

       exch2_pi(1,5,11)=1

       exch2_pi(2,5,11)=0

       INTEGER exch2_pi(2,MAX_NEIGHBOURS,NTILES)

     &        exch2_pi,exch2_pj,                  

       exch2_pi(2,1,127)=0

       exch2_pi(1,2,127)=1

       exch2_pi(2,2,127)=0

       exch2_pi(1,3,127)=1

       exch2_pi(2,3,127)=0

       exch2_pi(1,2,11)=1

       exch2_pi(2,2,11)=0

       exch2_pi(1,1,128)=1

       exch2_pi(2,1,128)=0

       exch2_pi(1,2,128)=1

       exch2_pi(2,2,128)=0

       exch2_pi(1,3,128)=1

       exch2_pi(2,3,128)=0

       exch2_pi(1,4,128)=1

       exch2_pi(2,4,128)=0

       exch2_pi(1,1,129)=1

       exch2_pi(2,1,129)=0

       exch2_pi(1,2,129)=1

       exch2_pi(2,2,129)=0

       exch2_pi(1,3,129)=1

       exch2_pi(2,3,129)=0

       exch2_pi(1,4,129)=1

       exch2_pi(2,4,129)=0

       exch2_pi(1,3,11)=1

       exch2_pi(2,3,11)=0

       exch2_pi(1,1,130)=1

       exch2_pi(2,1,130)=0

       exch2_pi(1,2,130)=1

       exch2_pi(2,2,130)=0

       exch2_pi(1,3,130)=1

       exch2_pi(2,3,130)=0

       exch2_pi(1,4,130)=1

       exch2_pi(2,4,130)=0

       exch2_pi(1,1,131)=1

       exch2_pi(2,1,131)=0

       exch2_pi(1,2,131)=1

       exch2_pi(2,2,131)=0

       exch2_pi(1,3,131)=1

       exch2_pi(2,3,131)=0

       exch2_pi(1,4,131)=0

       exch2_pi(1,4,11)=1

       exch2_pi(2,4,131)=1

       exch2_pi(2,4,11)=0

       exch2_pi(1,1,132)=1

       exch2_pi(2,1,132)=0

       exch2_pi(1,2,132)=1

       exch2_pi(2,2,132)=0

       exch2_pi(1,3,132)=1

       exch2_pi(2,3,132)=0

       exch2_pi(1,4,132)=1

       exch2_pi(2,4,132)=0

       exch2_pi(1,1,133)=1

       exch2_pi(2,1,133)=0

       exch2_pi(1,2,133)=1

       exch2_pi(2,2,133)=0

       exch2_pi(1,3,133)=1

       exch2_pi(2,3,133)=0

       exch2_pi(1,4,133)=1

       exch2_pi(2,4,133)=0

       exch2_pi(1,1,134)=1

       exch2_pi(2,1,134)=0

       exch2_pi(1,2,134)=1

       exch2_pi(2,2,134)=0

       exch2_pi(1,3,134)=1

       exch2_pi(2,3,134)=0

       exch2_pi(1,4,134)=1

       exch2_pi(2,4,134)=0

       exch2_pi(1,1,135)=1

       exch2_pi(2,1,135)=0

       exch2_pi(1,2,135)=1

       exch2_pi(2,2,135)=0

       exch2_pi(1,3,135)=1

       exch2_pi(2,3,135)=0

       exch2_pi(1,4,135)=0

       exch2_pi(2,4,135)=1

       exch2_pi(1,1,12)=1

       exch2_pi(1,1,136)=1

       exch2_pi(2,1,136)=0

       exch2_pi(2,1,12)=0

       exch2_pi(1,2,136)=1

       exch2_pi(2,2,136)=0

       exch2_pi(1,3,136)=1

       exch2_pi(2,3,136)=0

       exch2_pi(1,4,136)=1

       exch2_pi(2,4,136)=0

       exch2_pi(1,1,137)=1

       exch2_pi(2,1,137)=0

       exch2_pi(1,2,137)=1

       exch2_pi(2,2,137)=0

       exch2_pi(1,3,137)=1

       exch2_pi(2,3,137)=0

       exch2_pi(1,1,138)=1

       exch2_pi(1,2,12)=1

       exch2_pi(2,1,138)=0

       exch2_pi(2,2,12)=0

       exch2_pi(1,2,138)=1

       exch2_pi(2,2,138)=0

       exch2_pi(1,3,138)=1

       exch2_pi(2,3,138)=0

       exch2_pi(1,4,138)=1

       exch2_pi(2,4,138)=0

       exch2_pi(1,1,139)=1

       exch2_pi(2,1,139)=0

       exch2_pi(1,2,139)=1

       exch2_pi(2,2,139)=0

       exch2_pi(1,3,139)=1

       exch2_pi(2,3,139)=0

       exch2_pi(1,4,139)=0

       exch2_pi(2,4,139)=1

       exch2_pi(1,3,12)=1

       exch2_pi(1,1,140)=1

       exch2_pi(2,3,12)=0

       exch2_pi(2,1,140)=0

       exch2_pi(1,2,140)=1

       exch2_pi(2,2,140)=0

       exch2_pi(1,3,140)=1

       exch2_pi(2,3,140)=0

       exch2_pi(1,1,141)=1

       exch2_pi(2,1,141)=0

       exch2_pi(1,2,141)=1

       exch2_pi(2,2,141)=0

       exch2_pi(1,3,141)=1

       exch2_pi(2,3,141)=0

       exch2_pi(1,1,142)=0

       exch2_pi(2,1,142)=-1

       exch2_pi(1,4,12)=1

       exch2_pi(1,2,142)=0

       exch2_pi(2,2,142)=-1

       exch2_pi(2,4,12)=0

       exch2_pi(1,3,142)=1

       exch2_pi(2,3,142)=0

       exch2_pi(1,4,142)=1

       exch2_pi(2,4,142)=0

       exch2_pi(1,5,142)=0

       exch2_pi(2,5,142)=1

       exch2_pi(1,1,143)=0

       exch2_pi(2,1,143)=-1

       exch2_pi(1,2,143)=0

       exch2_pi(2,2,143)=-1

       exch2_pi(1,3,143)=1

       exch2_pi(2,3,143)=0

       exch2_pi(1,4,143)=1

       exch2_pi(2,4,143)=0

       exch2_pi(1,1,144)=0

       exch2_pi(2,1,144)=-1

       exch2_pi(1,2,144)=0

       exch2_pi(2,2,144)=-1

       exch2_pi(1,3,144)=1

       exch2_pi(2,3,144)=0

       exch2_pi(1,4,144)=1

       exch2_pi(2,4,144)=0

       exch2_pi(1,1,145)=1

       exch2_pi(2,1,145)=0

       exch2_pi(1,2,145)=0

       exch2_pi(2,2,145)=-1

       exch2_pi(1,3,145)=0

       exch2_pi(2,3,145)=-1

       exch2_pi(1,4,145)=1

       exch2_pi(2,4,145)=0

       exch2_pi(1,5,145)=1

       exch2_pi(2,5,145)=0

       exch2_pi(1,1,146)=1

       exch2_pi(2,1,146)=0

       exch2_pi(1,1,13)=1

       exch2_pi(1,2,146)=0

       exch2_pi(2,2,146)=-1

       exch2_pi(2,1,13)=0

       exch2_pi(1,3,146)=0

       exch2_pi(2,3,146)=-1

       exch2_pi(1,4,146)=1

       exch2_pi(2,4,146)=0

       exch2_pi(1,5,146)=1

       exch2_pi(2,5,146)=0

       exch2_pi(1,1,147)=1

       exch2_pi(2,1,147)=0

       exch2_pi(1,2,147)=0

       exch2_pi(2,2,147)=-1

       exch2_pi(1,3,147)=0

       exch2_pi(2,3,147)=-1

       exch2_pi(1,4,147)=1

       exch2_pi(2,4,147)=0

       exch2_pi(1,5,147)=1

       exch2_pi(2,5,147)=0

       exch2_pi(1,2,13)=1

       exch2_pi(2,2,13)=0

       exch2_pi(1,1,148)=1

       exch2_pi(2,1,148)=0

       exch2_pi(1,2,148)=0

       exch2_pi(2,2,148)=-1

       exch2_pi(1,3,148)=0

       exch2_pi(2,3,148)=-1

       exch2_pi(1,4,148)=0

       exch2_pi(2,4,148)=1

       exch2_pi(1,5,148)=1

       exch2_pi(2,5,148)=0

       exch2_pi(1,1,149)=1

       exch2_pi(2,1,149)=0

       exch2_pi(1,2,149)=1

       exch2_pi(2,2,149)=0

       exch2_pi(1,3,13)=1

       exch2_pi(1,3,149)=1

       exch2_pi(2,3,149)=0

       exch2_pi(2,3,13)=0

       exch2_pi(1,4,149)=1

       exch2_pi(2,4,149)=0

       exch2_pi(1,1,150)=1

       exch2_pi(2,1,150)=0

       exch2_pi(1,2,150)=1

       exch2_pi(2,2,150)=0

       exch2_pi(1,3,150)=1

       exch2_pi(2,3,150)=0

       exch2_pi(1,4,150)=1

       exch2_pi(2,4,150)=0

       exch2_pi(1,1,151)=1

       exch2_pi(2,1,151)=0

       exch2_pi(1,2,151)=1

       exch2_pi(2,2,151)=0

       exch2_pi(1,3,151)=1

       exch2_pi(2,3,151)=0

       exch2_pi(1,4,151)=1

       exch2_pi(2,4,151)=0

       exch2_pi(1,1,152)=1

       exch2_pi(2,1,152)=0

       exch2_pi(1,2,152)=1

       exch2_pi(2,2,152)=0

       exch2_pi(1,3,152)=0

       exch2_pi(2,3,152)=1

       exch2_pi(1,4,152)=1

       exch2_pi(2,4,152)=0

       exch2_pi(1,1,153)=1

       exch2_pi(2,1,153)=0

       exch2_pi(1,2,153)=1

       exch2_pi(2,2,153)=0

       exch2_pi(1,3,153)=1

       exch2_pi(2,3,153)=0

       exch2_pi(1,4,153)=1

       exch2_pi(2,4,153)=0

       exch2_pi(1,1,14)=1

       exch2_pi(2,1,14)=0

       exch2_pi(1,1,154)=1

       exch2_pi(2,1,154)=0

       exch2_pi(1,2,154)=1

       exch2_pi(2,2,154)=0

       exch2_pi(1,3,154)=1

       exch2_pi(2,3,154)=0

       exch2_pi(1,4,154)=1

       exch2_pi(2,4,154)=0

       exch2_pi(1,1,155)=1

       exch2_pi(2,1,155)=0

       exch2_pi(1,2,155)=1

       exch2_pi(2,2,155)=0

       exch2_pi(1,3,155)=1

       exch2_pi(2,3,155)=0

       exch2_pi(1,4,155)=1

       exch2_pi(1,2,14)=1

       exch2_pi(2,4,155)=0

       exch2_pi(2,2,14)=0

       exch2_pi(1,1,156)=1

       exch2_pi(2,1,156)=0

       exch2_pi(1,2,156)=1

       exch2_pi(2,2,156)=0

       exch2_pi(1,3,156)=0

       exch2_pi(2,3,156)=1

       exch2_pi(1,4,156)=1

       exch2_pi(2,4,156)=0

       exch2_pi(1,1,157)=1

       exch2_pi(2,1,157)=0

       exch2_pi(1,2,157)=1

       exch2_pi(2,2,157)=0

       exch2_pi(1,3,157)=1

       exch2_pi(2,3,157)=0

       exch2_pi(1,3,14)=1

       exch2_pi(1,4,157)=1

       exch2_pi(2,3,14)=0

       exch2_pi(2,4,157)=0

       exch2_pi(1,1,158)=1

       exch2_pi(2,1,158)=0

       exch2_pi(1,2,158)=1

       exch2_pi(2,2,158)=0

       exch2_pi(1,3,158)=1

       exch2_pi(2,3,158)=0

       exch2_pi(1,4,158)=1

       exch2_pi(2,4,158)=0

       exch2_pi(1,1,159)=1

       exch2_pi(2,1,159)=0

       exch2_pi(1,2,159)=1

       exch2_pi(2,2,159)=0

       exch2_pi(1,4,14)=1

       exch2_pi(1,3,159)=1

       exch2_pi(2,3,159)=0

       exch2_pi(2,4,14)=0

       exch2_pi(1,4,159)=1

       exch2_pi(2,4,159)=0

       exch2_pi(1,1,160)=1

       exch2_pi(2,1,160)=0

       exch2_pi(1,2,160)=1

       exch2_pi(2,2,160)=0

       exch2_pi(1,3,160)=0

       exch2_pi(2,3,160)=1

       exch2_pi(1,4,160)=1

       exch2_pi(2,4,160)=0

       exch2_pi(1,1,161)=1

       exch2_pi(2,1,161)=0

       exch2_pi(1,2,161)=1

       exch2_pi(2,2,161)=0

       exch2_pi(1,3,161)=1

       exch2_pi(2,3,161)=0

       exch2_pi(1,4,161)=1

       exch2_pi(2,4,161)=0

       exch2_pi(1,1,162)=1

       exch2_pi(2,1,162)=0

       exch2_pi(1,2,162)=1

       exch2_pi(2,2,162)=0

       exch2_pi(1,3,162)=1

       exch2_pi(2,3,162)=0

       exch2_pi(1,4,162)=1

       exch2_pi(2,4,162)=0

       exch2_pi(1,1,163)=1

       exch2_pi(2,1,163)=0

       exch2_pi(1,2,163)=1

       exch2_pi(2,2,163)=0

       exch2_pi(1,3,163)=1

       exch2_pi(2,3,163)=0

       exch2_pi(1,4,163)=1

       exch2_pi(2,4,163)=0

       exch2_pi(1,1,15)=1

       exch2_pi(2,1,15)=0

       exch2_pi(1,1,164)=1

       exch2_pi(2,1,164)=0

       exch2_pi(1,2,164)=1

       exch2_pi(2,2,164)=0

       exch2_pi(1,3,164)=0

       exch2_pi(2,3,164)=1

       exch2_pi(1,4,164)=1

       exch2_pi(2,4,164)=0

       exch2_pi(1,1,165)=1

       exch2_pi(2,1,165)=0

       exch2_pi(1,2,165)=1

       exch2_pi(2,2,165)=0

       exch2_pi(1,3,165)=1

       exch2_pi(2,3,165)=0

       exch2_pi(1,4,165)=1

       exch2_pi(1,2,15)=1

       exch2_pi(2,4,165)=0

       exch2_pi(2,2,15)=0

       exch2_pi(1,1,166)=1

       exch2_pi(2,1,166)=0

       exch2_pi(1,2,166)=1

       exch2_pi(2,2,166)=0

       exch2_pi(1,3,166)=1

       exch2_pi(2,3,166)=0

       exch2_pi(1,4,166)=1

       exch2_pi(2,4,166)=0

       exch2_pi(1,1,167)=1

       exch2_pi(2,1,167)=0

       exch2_pi(1,2,167)=1

       exch2_pi(2,2,167)=0

       exch2_pi(1,3,167)=1

       exch2_pi(2,3,167)=0

       exch2_pi(1,3,15)=1

       exch2_pi(1,4,167)=1

       exch2_pi(2,3,15)=0

       exch2_pi(2,4,167)=0

       exch2_pi(1,1,168)=1

       exch2_pi(2,1,168)=0

       exch2_pi(1,2,168)=1

       exch2_pi(2,2,168)=0

       exch2_pi(1,3,168)=0

       exch2_pi(2,3,168)=1

       exch2_pi(1,4,168)=1

       exch2_pi(2,4,168)=0

       exch2_pi(1,1,169)=1

       exch2_pi(2,1,169)=0

       exch2_pi(1,2,169)=1

       exch2_pi(2,2,169)=0

       exch2_pi(1,4,15)=1

       exch2_pi(1,3,169)=1

       exch2_pi(2,3,169)=0

       exch2_pi(2,4,15)=0

       exch2_pi(1,4,169)=1

       exch2_pi(2,4,169)=0

       exch2_pi(1,1,170)=1

       exch2_pi(2,1,170)=0

       exch2_pi(1,2,170)=1

       exch2_pi(2,2,170)=0

       exch2_pi(1,3,170)=1

       exch2_pi(2,3,170)=0

       exch2_pi(1,4,170)=1

       exch2_pi(2,4,170)=0

       exch2_pi(1,1,171)=1

       exch2_pi(2,1,171)=0

       exch2_pi(1,2,171)=1

       exch2_pi(2,2,171)=0

       exch2_pi(1,3,171)=1

       exch2_pi(2,3,171)=0

       exch2_pi(1,4,171)=1

       exch2_pi(2,4,171)=0

       exch2_pi(1,1,172)=1

       exch2_pi(2,1,172)=0

       exch2_pi(1,2,172)=1

       exch2_pi(2,2,172)=0

       exch2_pi(1,3,172)=0

       exch2_pi(2,3,172)=1

       exch2_pi(1,4,172)=1

       exch2_pi(2,4,172)=0

       exch2_pi(1,1,173)=1

       exch2_pi(2,1,173)=0

       exch2_pi(1,2,173)=1

       exch2_pi(2,2,173)=0

       exch2_pi(1,3,173)=1

       exch2_pi(2,3,173)=0

       exch2_pi(1,4,173)=1

       exch2_pi(2,4,173)=0

       exch2_pi(1,1,16)=1

       exch2_pi(2,1,16)=0

       exch2_pi(1,1,174)=1

       exch2_pi(2,1,174)=0

       exch2_pi(1,2,174)=1