/in/foo.cc: In function 'void Tarjan(int)':
/in/foo.cc:13:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0;i<linker[u].size();i++)
                 ~^~~~~~~~~~~~~~~~~
/in/foo.cc: In function 'int work()':
/in/foo.cc:39:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<linker[i].size();++j)
               ~^~~~~~~~~~~~~~~~~
/in/foo.cc:57:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^