function main(input = '') {
  if (!input) throw Error;

  return Array.from(input).reduce((result, c) => {
    console.log(c);

    if (c === c.toLowerCase()) {
      return result + c.toUpperCase();
    } else {
      return result + c.toLowerCase();
    }
  }, '');
}

const { readFileSync, existsSync } = require('fs');
const stdin = '/dev/stdin';

if (existsSync(stdin)) {
  const input = readFileSync(stdin, 'utf8');
  console.log(main(input));
}

module.exports = main;