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
def MinString():
    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))
MinString()