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 have_less(x, ch):
    for k in range(ord(ch) - ord('a') - 1, -1, -1):
        if x[k] > 0:
            return True
    return False


s = input()
t, u = [], []

stat = [0] * 26
for ch in s:
    stat[ord(ch) - ord('a')] += 1

pos = 0
while pos < len(s):
    if len(t) == 0:
        stat[ord(s[pos]) - ord('a')] -= 1
        t.append(s[pos])
        pos += 1
    while pos < len(s) and have_less(stat, t[-1]):
        t.append(s[pos])
        stat[ord(s[pos]) - ord('a')] -= 1
        pos += 1
    u.append(t.pop())

print(''.join(u) + ''.join(t[::-1]))