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()
dic = {}
t = []
u = ""
for i in s:
  if i in dic:
    dic[i] = dic[i] + 1
  else:
    dic[i] =1
j ='a';
for i in s:
  while((j not in dic) or dic[j]==0):
     j = chr(ord(j) + 1)
  if (len(t) >0):
    last_t = t[-1]
    while(ord(j) >= ord(last_t)):
      u = u+last_t
      t.pop()
      if (len(t)==0):
        break
      last_t = t[-1]
  t.append(i)
  dic[i] = dic[i] - 1
len_t = len(t)
for i in range(len_t):
  u =  u + t.pop()
print(u)