/in/foo.cc: In function 'int bfs_1(int, int)':
/in/foo.cc:29:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i=0;i<c.size();i++)
                      ~^~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:54:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int i=0;i<c.size();i++)
                      ~^~~~~~~~~