Compilare: user.cpp: In function ‘int main()’: user.cpp:29:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A.size(); i++) ~~^~~~~~~~~~ user.cpp:41:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A.size(); i++) ~~^~~~~~~~~~ user.cpp:50:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = A.size(); i < B.size(); i++) ~~^~~~~~~~~~