Compilare: user.cpp: In function ‘std::pair<int, int> intersect(std::vector<std::pair<int, int> >, std::vector<std::pair<int, int> >)’: user.cpp:24:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i + 1 < b.size()) ^ user.cpp:33:1: warning: control reaches end of non-void function [-Wreturn-type] } ^