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
ct = [0]*26

string = input()

for s in string:
	ct[ord(s)-ord('a')]+=1


t = []
u = []

for s in string:
	t.append(s)
	ct[ord(s)-ord('a')] -= 1
	# to get lexo minimal all previous chars must be already
	# part of final string
	while t and sum(ct[:ord(t[-1])-ord('a')])==0:
		u.append(t.pop())

print(*u,sep="")