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