Compilare: user.cpp: In function ‘void Back(int, long long int)’: user.cpp:14:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (num == prime.size()) ^ user.cpp: In function ‘int main()’: user.cpp:62:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^