Compilare: user.cpp: In function ‘int main()’: user.cpp:70:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < X.size() - 1; ++i) ^ user.cpp:72:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = X.size() - 1; i < Y.size(); ++i) ^ user.cpp:77:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < Y.size(); ++i) ^ user.cpp:80:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = Y.size() + 1; i < X.size(); ++i) ^