Compilare: main.cpp: In function 'int main()': main.cpp:27:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 27 | for (j=0; j<v[i].size (); j+=2) | ~^~~~~~~~~~~~~ main.cpp:30:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 30 | for (j=0; j<v[0].size (); j++) | ~^~~~~~~~~~~~~