fun lazy (f) {
  local flag = 0, value = 0;

  return fun () {
    if flag
    then return value
    else
      value := f ();
      flag  := 1;
      return value
    fi
  }
}

local l = lazy (fun () {write (1); return 800});
local x = read ();

write (l ());
write (l ())