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 = list(input())
t = list()
u = list()
d = dict()
var = 97
for i in range(26):
    d[chr(var + i)] = 0
for i in s:
    d[i] += 1
i = 0
while i < len(s):
    if d[chr(var)] > 0:
        while i < len(s):
            d[s[i]] -= 1
            t.append(s[i])
            i += 1
            if t[-1] <= chr(var):
                u.append(t.pop())
                break
    else:
        var += 1
        while t and t[-1] <= chr(var):
            u.append(t.pop())


while t != []:
    u.append(t.pop())

print("".join(u))
