#include <stdio.h>
int main() {
    int n, i, dem = 0;
    printf("Nhap n: ");
    scanf_s("%d", &n);
    if (n <= 1) {
        printf("Khong phai so nguyen to\n");
        return 0;
    }
    for (i = 2; i <= n / 2; i++) {
        if (n % i == 0) {
            dem++;
        }
    }
    if (dem == 0)
        printf("Day la so nguyen to");
    else
        printf("Khong phai so nguyen to");
    return 0;
}