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
s = list(raw_input())

stk = []

gre = ['z'] * len(s)
gre[-1] = s[-1]
for i in reversed( range(0, len(s) - 1) ):
	gre[i] = min(s[i], gre[i+1])

ans = []
for i, c in enumerate(s):
	if gre[i] == c:
		ans.append(c)
		while len(stk) > 0 and i+1 < len(s) and stk[-1] <= gre[i+1]:
			ans.append(stk.pop())
	else:
		stk.append(c)

while len(stk) > 0:
	ans.append(stk.pop())

print ''.join(ans)
