module Fibonacci;
  open import Stdlib.Prelude;

  fib :       ;
  fib zero x1 _  x1;
  fib (suc n) x1 x2  fib n x2 (x1 + x2);

  fibonacci :   ;
  fibonacci n  fib n 0 1;

  main : IO;
  main  putStrLn (natToStr (fibonacci 25));
end;