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
def place(c): return ord(c) - ord('a')
s, stk, res, freq = input(), [], [], [0 for i in range(26)]
for c in s: freq[place(c)] += 1
for c in s:
    freq[place(c)], isLowAvailable, _ = freq[place(c)] - 1, False, stk.append(c)
    while stk and not isLowAvailable:
        for i in range(place(stk[-1])-1, -1, -1):
            if freq[i]: isLowAvailable = True
        if not isLowAvailable: res.append(stk.pop())
while stk: res.append(stk.pop())
print("".join(res))