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 go(cnt,n):
    for i in range(0,n):
        if cnt[i]>0:
            return 1
    return 0
s=input()
n=len(s)
t=[];u=[]
cnt=[0]*26
for i in s:
    cnt[ord(i)-97]+=1
#print(cnt)
for i in range(n):
    if len(t)==0 or t[-1]>=s[i]:
        t.append(s[i])
    else:
        for j in reversed(t):
            if go(cnt,ord(j)-97)==0:
                u.append(j)
                t.pop()
            else: break
        t.append(s[i])
    cnt[ord(s[i])-97]-=1
print(''.join(u+t[::-1]))
    