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 collections import defaultdict
s = input()
n = len(s)
d = defaultdict(int)
for i in range(n):
    d[s[i]] += 1
stack = []
ans = ""
for i in range(n):
    stack.append(s[i])
    d[s[i]]-=1
    ok = True
    # print(stack)
    while(ok and stack):
        ok = False
        rem = True
        for j in range(ord('a'), ord(stack[-1])):
            char = chr(j)
            # print(char)
            if(d[char]):
                rem = False
                break
        if(rem):
            ok = True
            ans += stack[-1]
            stack.pop()
print(ans)