'''
回文质数：从左到右和从右到左是看一样的，比如151，11等，而且这个数必须为质数
'''



def is_num_prime(num):
    if num <= 1 or num%2==0:
        return False
    if num == 2:
        return True
    count = 0
    for n in range(3, int(num ** (1 / 2) + 1), 2):
        if num % n == 0:
            count = 1
    return True if count == 0 else False


def is_num_huiwei_prime(num):
    return True if str(num)[::-1] == str(num) else False


def main():
    a = int(input(''))
    b = int(input(''))
    start, end = (a, b) if a < b else (b, a)
    if start%2==0:
        start+=1
    for num in range(start, end + 1,2):
        if len(str(num)) % 2 == 0 and num!=11:
            continue
        elif num>9989899:
            break
        elif is_num_huiwei_prime(num):
             if is_num_prime(num):
                print(num, end='\n')
             else:
                 continue
if __name__ == '__main__':
    main()