/in/foo.cc: In function 'void MCMF(int, int)':
/in/foo.cc:59:22: warning: operation on 'i' may be undefined [-Wsequence-point]
   for (int i=e;i!=s;i=i=edge[((pre[i]-1)^1)+1].to)
                     ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/in/foo.cc:61:22: warning: operation on 'i' may be undefined [-Wsequence-point]
   for (int i=e;i!=s;i=i=edge[((pre[i]-1)^1)+1].to)
                     ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~