Compilare: main.cpp: In function 'int main()': main.cpp:55:32: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 55 | for ( j = 0; j < f[i].size(); j++ ) | ~~^~~~~~~~~~~~~