Compilare: main.cpp: In function 'void read(std::vector<std::vector<int> >&)': main.cpp:39:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 39 | for (int i = 0; i < m.size(); i++) | ~~^~~~~~~~~~ main.cpp:41:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 41 | for (int j = 0; j < m[i].size(); j++) | ~~^~~~~~~~~~~~~