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
ls=[0]*26

def getFirst():
    for i in range(0,26):
        if ls[i]>0:
            return i
def remover(i):
    ls[i]-=1

s=input()
c={}
for i in s:
    n = ord(i) - 97 
    if n in c:
        c[n]+=1
    else:
        c[n]=1
ks=[*c]

for i in ks:
    ls[i]=c[i]
stack=[]
ans=""
i=int(0)
while(i<len(s)):
    f=getFirst()
    
    n=ord(s[i])-97
    if (len(stack)!=0):
        if(ord(stack[len(stack)-1])-97<=f):
            ans+=stack.pop()
            i-=1
        else:
            stack.append(s[i])
            remover(n)
    else:
        stack.append(s[i])
        remover(n)
    i+=1
while len(stack)>0:
    a=stack.pop()
    ans+=a
print(ans)