manage.js
function mod(x, by) {
    return (x > 0) ? x % by
           : (by - (Math.abs(x) % by)) % by
  }
function mod(x, by) {
    return (x > 0) ? x % by
           : (by - (Math.abs(x) % by)) % by
  }
console.log('root: ', root)