int N;
cout << "请输入整数：";
cin >> N;

bool Flag = false;

if (N >= 2){
  Flag = true;
  for (int i=2; i < N; i++)
   if (N % i == 0){
    Flag = false;
    break;
   }
}

if(Flag)
  cout << "是质数";
else
  cout << "不是质数";