Compilare: main.cpp: In function 'void combine(std::vector<std::pair<int, int> >&, std::vector<std::pair<int, int> >&)': main.cpp:32:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < b.size() && b[i].first < it.first) { ~~^~~~~~~~~~ main.cpp:36:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i < b.size() && b[i].first == it.first) { ~~^~~~~~~~~~ main.cpp:43:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < b.size()) { ~~^~~~~~~~~~