void fibo(unsigned int x, unsigned int *fib)
{
  unsigned int f0, f1, f, k;
  
  f0 = 0;
  f1 = 1;
  
  if (x <= 0)
  {
    f = f0;
  }
  else if (x == 1)
  {
    f = f1;
  }
  else
  {
    for (k = 2; k <= x; k = k + 1)
    {
      f = f1 + f0;
      f0 = f1;
      f1 = f;
    }
  }
  *fib = f;  
}