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()

al=[0]*27
for e in s:
    al[ord(e)-96]+=1
#print(al)
t=[]
ans=''
for e in range(len(s)):
    t.append(s[e])
    al[ord(s[e])-96]-=1
    while e<len(s)-1 and t and sum(al[:(ord(t[-1])-96)])==0:
        ans+=t[-1]
        t.pop()
while t:
    ans+=t[-1]
    t.pop()
print(ans)