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()

t = list()

ans = ""

index = 0

for character in "abcdefghijklmnopqrstuvwxyz":
    
    while len(t) > 0 and t[-1] <= character:
        
        ans += t[-1]
        
        t.pop()
        
    pos = s.find(character, index)
    
    while pos >= 0:
        
        while index < pos:
            
            t.append(s[index])
            
            index += 1
            
        ans += character
        
        index += 1
        
        pos = s.find(character, index)
        
while len(t) > 0:
        
    ans += t[-1]
        
    t.pop()
        
print(ans)