JHK (whose true name shall not be revealed) is one of Mr. Ing's favourite students. In light of the recent successful defense of the Ingdom, JHK decides to celebrate by preparing for this year's Putnam contest. On week one of his Seven Week Challenge, JHK decides he wants to study prime numbers. Write a program to help him solve the following problem.
Define the Junghoon-value (or the for short) of a positive integer to be the least number of primes (not necessarily distinct) required to yield a sum of . For example, the number can be formed using the primes OR , therefore its is 2. Note: If no combination of primes sum to , its is undefined.
Junghoon JHK find the number of positive integers less than or equal to with of exactly .
One line containing two space-separated integers and .
Print the number of positive integers less than or equal to with of exactly .
It would be helpful to know Sieve of Eratosthenes.