Compilare: user.cpp: In function ‘void read()’: user.cpp:16:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<=M;i++) ^ user.cpp: In function ‘void solve()’: user.cpp:29:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<=N;i++) ^ user.cpp:31:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<G[i].size();j++) ^