/in/foo.cc: In function 'void BellmanFord()':
/in/foo.cc:15:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int j=0;j<to[i].size();j++)
                ~^~~~~~~~~~~~~
/in/foo.cc:12:7: warning: unused variable 'flag' [-Wunused-variable]
  bool flag=false;
       ^~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:30:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int j=0;j<realw[i].size();j++)
                ~^~~~~~~~~~~~~~~~