/in/foo.cc: In function 'bool DFS(int, int)':
/in/foo.cc:24:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
       for(int i=0;i<v.size();i++)
                   ~^~~~~~~~~
/in/foo.cc:30:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<v.size();i++)
              ~^~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:45:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<ans.size();i++)
              ~^~~~~~~~~~~