Compilare: main.cpp: In function 'std::vector<std::vector<int> > prod(std::vector<std::vector<int> >, std::vector<std::vector<int> >)': main.cpp:17:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 17 | for (int i=0; i<rez.size(); i++) | ~^~~~~~~~~~~ main.cpp:19:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 19 | for (int i=0; i<a.size(); i++) | ~^~~~~~~~~ main.cpp:21:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 21 | for (int j=0; j<b[0].size(); j++) | ~^~~~~~~~~~~~ main.cpp:23:28: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 23 | for (int k=0; k<a[0].size(); k++) | ~^~~~~~~~~~~~