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 = raw_input().split()[0]
stack = []
u = []
minimum = [('',-1)]*len(s)
minimum[-1] = (s[-1],len(s)-1)
for i in xrange(len(s)-2,-1,-1):
	minimum[i] = (s[i],i) if s[i] <= minimum[i+1][0] else minimum[i+1]
for i in xrange(len(s)):
	stack.append(i)
	if minimum[i][1] == i:
		u.append(s[stack.pop()])
	while i < len(s) - 1 and len(stack) > 0 and minimum[i+1][0] >= s[stack[-1]]:
		u.append(s[stack.pop()])
while len(stack) > 0:
	u.append(s[stack.pop()])
print ''.join(u)