void
fib (int n)
{
  static int a;
  a = 1;
  static int b;
  b = 1;
  static int i;
  i = 3;
  if (i <= n)
    do
      {
	c = a + b;
	a = b;
	b = c;
	i = i + 1;
      }
    while (i <= n);
  printf ("%d\n", b);
}