/in/foo.cc: In function 'int dfs(int, int)':
/in/foo.cc:45:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<v[a].size();i++)
                     ~^~~~~~~~~~~~
/in/foo.cc: In function 'void safe()':
/in/foo.cc:77:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<s[h].size();i++)
                     ~^~~~~~~~~~~~
/in/foo.cc: In function 'void spfa()':
/in/foo.cc:97:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i=0;i<v[h].size();i++)
                     ~^~~~~~~~~~~~