/in/foo.cc: In function 'long long int f1(int)':
/in/foo.cc:16:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int k=0;k<g[i].size();k++)  
                 ~^~~~~~~~~~~~
/in/foo.cc: In function 'long long int f2(int)':
/in/foo.cc:31:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int k=0;k<gr[i].size();k++)  
                 ~^~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:59:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int k=0;k<g[i].size();k++)  
                     ~^~~~~~~~~~~~