Compilare: main.cpp: In function 'std::vector<long long int> multiply(const std::vector<long long int>&, const std::vector<std::vector<long long int> >&)': main.cpp:42:22: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::vector<long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 42 | for(int i = 0; i < m.size(); ++i) | ~~^~~~~~~~~~ main.cpp:43:26: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::vector<long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 43 | for(int j = 0; j < m.size(); ++j) | ~~^~~~~~~~~~