title: Generate Random number between two number with one rare number
body: <p>i can generate random number between two numbers in c using this..</p>
  
  <pre><code>arc4random()%(high-low+1)+low;
  </code></pre>
  
  <p>then now my requirement is...i want to make a number rare....thats mean if </p>
  
  <p>high=5,
  low=1, 
  and rare=3, </p>
  
  <p>than 3 will be appeared much rarely than 1,2,4 and 5...</p>
  
  <p>Thanks</p>