Petya recieved a gift of a string s with length up to 10^5 characters for his birthday. He took two more empty strings t and u and decided to play a game. This game has two possible moves:  Extract the first character of s and append t with this character.  Extract the last character of t and append u with this character. 

Petya wants to get strings s and t empty and string u lexicographically minimal.

You should write a program that will help Petya win the game.


-----Input-----

First line contains non-empty string s (1 ≤ |s| ≤ 10^5), consisting of lowercase English letters.


-----Output-----

Print resulting string u.


-----Examples-----
Input
cab

Output
abc

Input
acdb

Output
abdc