title: Represent a number as sum of primes
body: <p>I am given a large number <code>n</code> and I need to find whether it can be represented as sum of K prime numbers.</p>
  
  <p>Ex 9 can be represented as sum of 3 prime number as 2+2+5.</p>
  
  <p>I am trying to use variation of  subset sum but number is too large to generate all primes number till then.</p>
  
  <p>The problem is from the current <a href="https://www.hackerrank.com/contests/w3/challenges/prime-sum" rel="nofollow">HackerRank contest</a>. The restrictions are <code>1 &lt;= n, K &lt;= 10^12</code> </p>