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 solve():

	s = raw_input().strip()

	counta = [0] * 26
	for i in s:
		counta[ord(i) - 97] += 1

	t = []
	res = []


	for i in s:
		t.append(i)
		counta[ord(t[-1]) - 97] -= 1
		while t and sum(counta[:ord(t[-1]) - 97]) == 0:
			res.append(t.pop())

	while t:
		res.append(t.pop())
	print "".join(res)
solve()
