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()
u = ''
t = []
d1 = [0] * 26
d2 = [0] * 26
n = len(s)
a = ord('a')
for i in range(n):
    d1[ord(s[i]) - a] += 1

i = 0
for j in range(26):
    while i < n and d2[j] < d1[j]:
        if s[i] == chr(j + a):
            u += s[i]
            d2[j] += 1
        else:
            t.append(s[i])
            d2[ord(s[i]) - a] += 1
        i += 1

    for p in range(26):
        if d2[p] < d1[p]:
            q = p
            break
    else:
        q = 26

    while len(t) > 0 and t[-1] <= chr(q + a):
        k = t.pop(-1)
        u += k

print(u)