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()
c = ['z'] * (len(s) + 1)
for i in range(len(s)-1, -1, -1):
	c[i] = min(c[i+1], s[i])
st = list()
i = 0
while len(st) > 0 or i < len(s):
	if len(st) > 0 and st[len(st)-1] <= c[i]:
		print(st[len(st)-1], end = "")
		st.pop()
	else:
		st.append(s[i])
		i += 1
print()