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()
n=len(s)
freq=[0]*27
for i in range(n):
    freq[ord(s[i])+1-97]+=1
for i in range(1,27):
    freq[i]+=freq[i-1]
u,t=[],[]
for i in range(n):
    t.append(s[i])
    for i in range(ord(s[i])-97+1,27):
            freq[i]-=1
    while(len(t)>0 and freq[ord(t[-1])-97]<1):
        u.append(t.pop())
print(("").join(u))