Maga and Alex are good at string manipulation problems. Just now they have faced a problem related to string. But it is not a standard string problem. They have no idea to solve it. They need your help.

A string is called unique if all characters of string are distinct.

String \(s_1\) is called subsequence of string \(s_2\) if \(s_1\) can be produced from \(s_2\) by removing some characters of \(s_2\).

String \(s_1\) is stronger than \(s_2\) if \(s_1\) is lexicographically greater than \(s_2\).

You are given a string. Your task is to find the strongest unique string which is subsequence of given string.

Input:

first line contains length of string.
second line contains the string.

Output:

Output the strongest unique string which is subsequence of given string.

Constraints:

\(1 \le |S| \le 100000\)

All letters are lowercase English letters.