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
# https://codeforces.com/contest/797/problem/C
# wrong
from collections import OrderedDict


def getMinAlpha(freq):
    for i in freq:
        if freq[i] != 0:
            break
    return i


s = input()
t, u = [], []
freq = OrderedDict()
for i in range(1, 27):
    freq.update({chr(i+96): 0})
for i in range(len(s)):
    freq.update({s[i]: freq[s[i]]+1})
for i in range(len(s)):
    minElm = getMinAlpha(freq)
    while(len(t) > 0 and t[-1] <= minElm):
        u.append(t.pop())
    if s[i] == minElm:
        u.append(s[i])
    else:
        t.append(s[i])
    freq.update({s[i]: freq[s[i]]-1})
while(len(t) > 0):
    u.append(t.pop())
print("".join(u))
