New puzzle: Find a number with a number of 4s and 7s that has only 4s and 7s #9
Description
def sat(d: int): """ Find a number bigger than n whose decimal representation has k 4's and 7's where k's decimal representation consists only of 4's and 7's Inspired by [Codeforces Problem 110 A](https://codeforces.com/problemset/problem/110/A) """ return d > 123456789 and set(str(str(d).count("4") + str(d).count("7"))) <= {"4", "7"}Solvers, post your solutions in the comments using the following formatting:
<details><summary>Reveal solution</summary> ```python def sol(): return "world" # replace with your solution ``` </details>