Compilare: user.cpp: In function ‘int main()’: user.cpp:33:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A.size(); ++i) ^ user.cpp:37:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (j < A.size() && A[i].first == A[j].first) ^ user.cpp:47:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < result.size(); ++i) ^