/in/foo.cc: In function 'bool spfa(int, int)':
/in/foo.cc:31:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<g[he].size();i++){
               ~^~~~~~~~~~~~~
/in/foo.cc: In function 'int dfs(int, int, int)':
/in/foo.cc:45:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<g[x].size();i++){
              ~^~~~~~~~~~~~