import "io"

let twotimes(x) be
{ let sptr, prev;
  if x = 0 then resultis 0;
  prev := twotimes(x-1);
  resultis prev+2 }

let start() be
{ let a = 500;
  let b = twotimes(a);
  out("twotimes(%d) = %d\n", a, b) }