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 = input()
ls = len(s)
s1 = s[::-1]
d = dict()
t = list()
u = list()
sets = sorted(set(s))
setsl = len(sets)
for i in range(setsl):
    try:
        idx = s1.index(sets[i])
        if i==0:
            d[sets[i]] = (0, ls - idx - 1)
            prev = sets[i]
        elif ls - idx - 1>d[prev][1]:
            d[sets[i]] = (d[prev][1]+1, ls - idx - 1)
            prev = sets[i]
    except:
        pass
#print(d)
for i in d:
    while t and t[-1]<=i:
        u.append(t.pop())
    for j in range(d[i][0],d[i][1]+1):
        #print(i)
        #print(d[i][0],d[i][1]+1)
        if s[j]==i:
            u.append(s[j])
        else:
            t.append(s[j])
    

u = ''.join(u+t[::-1])
print(u)