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
import collections
inp=list(raw_input())
#print inp
dq=collections.deque(inp)
#print dq
stk=[]
coulis=[0]*26
#print inp
for cr in inp:
    coulis[ord(cr)-ord('a')]+=1
#print coulis
res=""
i=0
while len(dq):
    cmpcr=chr(97+i)
    cmpcou=coulis[i]
    for x in xrange(cmpcou):
        while stk != [] and stk[-1] <= cmpcr:
            res += stk.pop()
        try:
            while dq[0]!=cmpcr:
                stk.append(dq.popleft())
                coulis[ord(stk[-1])-ord('a')]-=1
            res+=dq.popleft()
        except:
            break
    i+=1
while stk!=[]:
    res+=stk.pop()
print res