Compilare: user.cpp: In function ‘bool f(int)’: user.cpp:14:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; x + i -1 <= b.size() && i < a.size(); i++) ^ user.cpp:14:56: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; x + i -1 <= b.size() && i < a.size(); i++) ^