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 = raw_input()
n = len(s)
m = s[-1]
l = ['']*n
l[-1] = m
for i in range(n-1)[::-1]:
    m = min(s[i],m)
    l[i] = m
ans = []
ns = []
for i in range(n):
    
    while ns!=[]:
        p = ns.pop()
        if p<=l[i]:
            ans.append(p)
        else:
            ns.append(p)
            break
    ns.append(s[i])
    '''
    if s[i]==l[i]:
        while ns!= []:
            p = ns.pop()
            if p<=s[i]:
                ans.append(p)
            else:
                ns.append(p)
                break   
        ans.append(s[i])
    else:
        ns.append(s[i])
    '''
while ns!=[]:
    ans.append(ns.pop())
print ''.join(ans)
