/in/foo.cc: In function 'bool spfa()':
/in/foo.cc:31:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<map[endi].size();i++)
              ~^~~~~~~~~~~~~~~~~
/in/foo.cc:41:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<map[bg].size();i++)
                 ~^~~~~~~~~~~~~~~
/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:60:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int i=0;i<map[x].size();i++)
                ~^~~~~~~~~~~~~~