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
sequence, stack, letter_count, ans = input(), [], [0] * 26, ''

# O(n)
for x in sequence:
    letter_count[ord(x) - 97] += 1

for x in sequence:
    stack.append(x)
    letter_count[ord(x) - 97] -= 1

    while stack and sum(letter_count[:ord(stack[-1]) - 97]) == 0:
        ans += stack.pop()
print(ans)