Compilare: user.cpp: In function ‘int main()’: user.cpp:16:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A.size(); i++) { ^ user.cpp:21:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A.size(); i++) { ^ user.cpp:26:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = A.size(); i < B.size(); i++) ^