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
s=input()
stack,res,k=[],[],[0]*26
for c in s:
    k[ord(c)-97]+=1
for c in s:
    stack.append(c)
    k[ord(c)-97]-=1
    while stack and sum(k[:(ord(stack[-1])-97)])==0:
        res.append(stack.pop())
print("".join(res))
