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 = []
u = ''
alphabets =list('abcdefghijklmnopqrstuvwxyz')
idx = 0
for c in alphabets:
    while t and t[-1]<=c:
        u = u + t.pop()
    try:
        nxt = s.index(c,idx)
    except ValueError:
        nxt = -1
    while (nxt>=0):
        while (idx<nxt):
            t.append(s[idx])
            idx+=1
        u = u + c
        idx+=1
        try:
            nxt = s.index(c,idx)
        except ValueError:
            nxt = -1
while t:
    u = u + t.pop()
print(u)
