title: Find the sum of all the multiples of 3 or 5 below 1000
body: <p>If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
  I have the following code but the answer does not match.</p>
  
  <pre><code>#include&lt;stdio.h&gt;
  int main()
  {
      long unsigned int i,sum=0;
      clrscr();
      for(i=0;i&lt;=1000;i++)
      {
          if((i%5==0)||(i%3==0))
          {
              sum=sum+1;
          }
      }
      printf("%d\n",sum);
      getchar();
      return 0;
  }
  </code></pre>