fn main() {

   fn fib(n: int) -> int {

     fn _fib(n: int, a: int, b: int) -> int {
       match (n, a, b) {
	 (0, _, _) => a,
	 _         => _fib(n-1, a+b, a)
       }
     }

     _fib(n, 0, 1)

   }

   for int::range(0,20) |n| {
     io::println(fmt!("%?", fib(n)))
   }
}