include

using namespace std;

int main () {

int i, b;

for (int i = 2; i <= 20; i++) {

	int s = 2;
	int f = 1;

	while (s <= i - 1) {

		if (i % s == 0) {
			f = 0;
		}

		s++;

	}

	if (f == 0) {
		cout << i << "不是质数" << endl;
	} else {
		cout << i << "是质数" << endl;
	}
}

return 0;

}