Given a natural number N, your task is to print the digits of the number as shown in the example [closed]

A magic number is a natural number that contains both the digits 7 and 9 in it. For eg:- 79, 879, 53729 etc.
Given a number N, your task is to find the closest Magic number from the given number N.

Note:- If more than one answer exists return the minimum one
Input
User Task:
Since this will be a functional problem, you don’t have to take input. You just have to complete the function MagicNumber() that takes integer N as argument.

Constraints:-
1 <= N <= 100000
Output
Return a magic number closest to the given number N.

Example.
Sample Input:-
8

Sample Output:-
79

Sample Input:-
900

Sample Output:-
897