
def is_prime(n):
    if n < 2:
        return False
    elif n == 2:
        return True
    elif n % 2 == 0:
        return False
    for i in range(3, n, 2):
        if n % i == 0:
            return False
    return True


def main():
    print(is_prime(1))
    print(is_prime(2))
    print(is_prime(8))
    print(is_prime(11))
    print(is_prime(-10))


if __name__ == '__main__':
    main()
