a, b = map(int, input().split()) def is_prime(x): for i in range(2, int(x ** 0.5) + 1): if x % i == 0: return False return True for i in range(a, b + 1): if i in [5, 7, 11]: print(i) elif len(str(i)) % 2 and str(i) == str(i)[::-1]: if is_prime(i): print(i) print(-1) 소수 판정