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
import string

def get_min(a):
    for ind, x in enumerate(a):
        if x:
            return chr(ind + ord('a'))
    return None


s = input()
al = [s.count(x) for x in string.ascii_lowercase]
stack = []
i = 0
while i < len(s):
    if stack and stack[-1] <= get_min(al):
        print(stack.pop(), end='')
        continue
    stack.append(s[i])
    if s[i] == get_min(al):
        print(stack.pop(), end='')
    al[ord(s[i]) - ord('a')] -= 1
    i += 1
for i in stack[-1::-1]:
    print(i, end='')
    