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
s=list((input()))
t=[]
u=[]
a=[[0 for i in range(26)]]
#print(a)
for i in range(len(s)-1,-1,-1):
    b=a[-1][:]
    a.append(b)
    a[-1][ord(s[i]) - ord('a')]=a[-2][ord(s[i]) - ord('a')] + 1
b=a[::-1]
j=0
i=0
while i<len(s):
    if b[i][j]==0:
        j+=1
        continue
    while len(t)>0 and ord(t[-1])<=(j+ord('a')):
        u.append(t.pop())
    if b[i][j]!=0:
        if s[i]==chr(j+ord('a')):
            u.append(s[i])
        else:
            t.append(s[i])
    else:
        j+=1
    i+=1    
    #print(i,j,u,t)    
while len(t)>0:
    u.append(t.pop())
print(''.join(u))
    