Compilare: user.cpp: In function ‘bool verifica(int)’: user.cpp:30:38: 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:30:54: 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: In function ‘int main()’: user.cpp:39:62: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i - 1 + a.size()<=b.size() && i < b.size(); i++) ^