Compilare: user.cpp: In function ‘int main()’: user.cpp:12:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<S.length();i++){ ^ user.cpp:15:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i == S.length()-1 || !((S[i+1] >= 'a' && S[i+1] <='z') || (S[i+1] >= 'A' && S[i+1] <='Z'))) num++; ^