/in/foo.cc: In function 'int main()':
/in/foo.cc:20:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=0;j<G[i].size();j++){
               ~^~~~~~~~~~~~
/in/foo.cc:16:20: warning: array subscript is above array bounds [-Warray-bounds]
        a[1000][1000]=0;
        ~~~~~~~~~~~~^
/in/foo.cc:16:14: warning: array subscript is above array bounds [-Warray-bounds]
        a[1000][1000]=0;
        ~~~~~~^