A prime number is a number which has exactly two distinct divisors: one and itself. For example, numbers 2, 7, 3 are prime, and 1, 6, 4 are not. The next prime number after x is the smallest prime number greater than x . For example, the next prime number after 2 is 3, and the next prime number after 3 is 5. Note that there is exactly one next prime number after each number. So 5 is not the next prime number for 2. One cold April morning Panoramix predicted that soon Kakofonix will break free from his straitjacket, and this will be a black day for the residents of the Gallic countryside. Panoramix's prophecy tells that if some day Asterix and Obelix beat exactly x Roman soldiers, where x is a prime number, and next day they beat exactly y Roman soldiers, where y is the next prime number after x , then it's time to wait for Armageddon, for nothing can shut Kakofonix up while he sings his infernal song. Yesterday the Gauls beat n Roman soldiers and it turned out that the number n was prime! Today their victims were a troop of m Romans ( m n ). Determine whether the Gauls should wait for the black day after today's victory of Asterix and Obelix?

输入描述:

The first and only input line contains two positive integers — n and m (2 ≤ n m ≤ 50). It is guaranteed that n is prime.Pretests contain all the cases with restrictions 2 ≤ n m ≤ 4.

输出描述:

Print YES, if m is the next prime number after n, or NO otherwise.