function beautifulTriplets(d, arr) {
  let ret = 0;
  for (let i = 0; i < arr.length - 2; i++) {
    const num = arr[i];
    if (arr.some(value => value === num + d) && arr.some(value => value === num + d * 2)) {
      ret++;
    }
  }
  return ret;
}