Compilare: main.cpp: In function 'std::vector<std::vector<int> > mult(std::vector<std::vector<int> >&, std::vector<std::vector<int> >&)': main.cpp:17:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < X.size(); i++ ) ~~^~~~~~~~~~ main.cpp:18:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int j = 0; j < Y[0].size(); j++ ){ ~~^~~~~~~~~~~~~ main.cpp:20:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int k = 0; k < X[i].size(); k++ ){ ~~^~~~~~~~~~~~~