1'use strict';
2function fib(n) {
3  if (n === 0 || n === 1) return n;
4  return fib(n - 1) + fib(n - 2);
5}
6
7const n = parseInt(process.env.FIB, 10) || 40;
8process.stdout.write(`${fib(n)}\n`);
9