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 = input().strip()
t=[]
u=[]
a = "abcdefghijklmnopqrstuvwxyz"
z = dict()
for i in a:
	z[i]=0
for i in s:
	z[i]+=1
for i in s:
	t.append(i)
	z[i]-=1
	while t:
		f=0
		top = t[-1]
		for j in z:
			if j<top and z[j]>0:
				f=1
				break
		if f==1:
			break
		else:
			u.append(t.pop())

while t:
	u.append(t.pop())
print(''.join(u))