A8104. Panoramix's Prediction

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?

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 $2<=n<m<=4$ .

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