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()
t=[]
u=[]
n=len(s)
a=[0]*26

for i in range(len(s)):
    z=ord(s[i])-97
    a[z]+=1

FirstLetterInS=0
LengthT=0
while len(u)!=n:
    if len(t)==0:
        a[ord(s[FirstLetterInS])-97]-=1
        z=s[FirstLetterInS]
        t.append(z)
        FirstLetterInS+=1
    else:
        flag=False
        x = -1
        for i in range(ord(t[-1])-97):
            if a[i]>0:
                flag=True
                break
        if flag:
            z=s[FirstLetterInS]
            t.append(z)
            FirstLetterInS+=1
            a[ord(z) - 97] -= 1
        else:
            u+=t[-1]
            t.pop()
print("".join(u))
