Compilare: user.cpp: In function ‘int calc(int, int, int)’: user.cpp:18:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<v[b].size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:50:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0; j < v[0].size(); j++) ^