Petya recieved a gift of a string s with length up to 105 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| ≤ 105), consisting of lowercase English letters.

Output

Print resulting string u.

Examples

Input

cab


Output

abc


Input

acdb


Output

abdc
from itertools import takewhile

def f(s):
    t = []
    u = []
    chars = 'abcdefghijklmnopqrstuvwxyz'

    for c in chars:
        stack = list(takewhile(lambda x: x <= c, reversed(t)))
        count = len(stack)
        if count > 0:
            u += stack
            t = t[:-count]

        count = s.count(c)
        if count > 0:
            rindex = s.rindex(c)
            u += c * count
            t += [x for x in s[:rindex] if x != c]
            s = s[rindex + 1:]

    u += reversed(t)
    return ''.join(u)

if __name__ == '__main__':
    print(f(input()))
