Compilare: main.cpp: In function 'int main()': main.cpp:39:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare] 39 | for (j = 0; j < l[vf.first].size(); j++) | ~~^~~~~~~~~~~~~~~~~~~~