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(raw_input())
lets = "abcdefghijklmnopqrstuvwxyz"
cnt = [0 for x in range(26)]
cur = 26
for i in s:
    cnt[lets.find(i)] += 1
    cur = min(cur,lets.find(i))
stk = []
stk2 = []
for i in s:
    temp = lets.find(i)
    cnt[temp] -= 1
    while stk2 and lets.find(stk2[-1])<=cur:
        stk.append(stk2.pop(-1))
    if temp==cur:
        stk.append(i)
    else:
        stk2.append(i)
    while cnt[cur]==0 and cur < 25:
        cur += 1
print "".join(stk+stk2[::-1])