Can anyone suggest me how to solve this problem(https://cses.fi/problemset/task/1087)

You are given a DNA sequence consisting of characters A, C, G, and T.

Your task is to find the shortest DNA sequence that is not a subsequence of the original sequence.

Input

The only input line contains a DNA sequence with n characters.

Output

Print the shortest DNA sequence that is not a subsequence of the original sequence. If there are several solutions, you may print any of them.

Constraints 1≤n≤1e6 Example

Input: ACGTACGT

Output: AAA