Compilare: main.cpp: In function 'int main()': main.cpp:62:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 62 | for (int i = 0; i < C.size(); ++ i) { | ~~^~~~~~~~~~ main.cpp:65:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 65 | for (int j = 0; j < C[i].size(); ++ j) | ~~^~~~~~~~~~~~~