title: Runtime Error (NZEC) in simple code
body: <p>I'm getting runtime error (NZEC) when running the following code over at SPOJ. I'd be very thankful if any of you would kindly point out what's going on.</p>
  
  <pre><code>//0&lt;=A&lt;=B&lt;=10^18, 1&lt;=N&lt;=10^18
  using System;
  class any
  {
  static void Main()
   {
      long t = long.Parse(Console.ReadLine());
      ulong a, b, n;
  
      for(long k = 0; k &lt; t; k++)
       {
          string[]s = Console.ReadLine().Split(' ');
          a = ulong.Parse(s[0]);
          b = ulong.Parse(s[1]);
          n = ulong.Parse(s[2]);
          Console.WriteLine(diviEntre2(a, b, n));
       }
   }
  static ulong diviEntre2(ulong f, ulong c, ulong n)
  {
     ulong k, s, m;
  
      if (f == c &amp;&amp; c % n == 0 &amp;&amp; f != 0) k = c/n;
  
      else
       {
        s = f/n;
        m = c/n;
  
        k = m - s;
       }
  
    return k;
  }
  }
  </code></pre>