Compilare: user.cpp: In function ‘bool f(int)’: user.cpp:14:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; x+i < b.size() && i < a.size(); i++) ^ user.cpp:14:51: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; x+i < b.size() && i < a.size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:23:60: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i + a.size() <= b.size() && i < b.size(); i++) ^