n = int(input("请输入一个正整数: "))
if n <= 1:
    print(f"{n}非素数")
elif n == 2:
    print("2是素数")
else:
    limit = int(n ** 0.5) + 1
    for i in range(2, limit):
        if n % i == 0:
            print(f"{n}非素数")
            break
    else:
        print(f"{n}是素数")