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()
n=len(s)
freq = [0]*26
if len(s)==0:
    print("")
for i in s:
    freq[ord(i)-ord("a")]+=1

stack=[]
ans = ""
for i in range(n):
    stack.append(s[i])
    freq[ord(s[i])-ord("a")]-=1
    flag = True
    while len(stack) and flag:
        for j in reversed(range(ord(stack[-1])-ord("a"))):
            if freq[j]>0:
                flag=False
        if flag:
            ans+=stack[-1]
            stack.pop()
print(ans)