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
RI = lambda : [int(x) for x in input().split()]
rw = lambda : [input().strip()]


s=list(input().strip())

stack=[]
index_stack=-1

ans=""

d={}
ch="abcdefghijklmnopqrstuvwxyz"
for i in ch:
    d[i]=0
for i in range(len(s)):
    d[s[i]]+=1

previous=-1#index of previous element added to ans
index=0
for i in d:
    #print(d[i])
    while(index_stack>=0 and stack[index_stack]<=i):
        ans+=stack[index_stack]
        stack.pop()
        index_stack-=1
    while(index!=len(s) and d[i]!=0):
        if(s[index]==i):
            ans+=i
            d[i]-=1
        else:
            stack.append(s[index])
            index_stack+=1
            d[s[index]]-=1
        index+=1

while(len(stack)!=0):
    ans+=stack[index_stack]
    index_stack-=1
    stack.pop()
print(ans)
        
    
    
