Compilare: user.cpp: In function ‘double solve()’: user.cpp:42:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); i++) ^ user.cpp:43:71: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = i + 1; a[j].first - a[i].first < d && j < a.size(); j++) ^