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 fnz(l):
    for i in range(len(l)):
        if l[i] != 0:
            return i
    return i
alphabets = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"]
count_alph = [0]*26
s = input()
t = []
u = []
for i in s:
    count_alph[alphabets.index(i)] +=1

for i in s:
    t.append(i)
    count_alph[alphabets.index(i)] -=1
    while t[-1] <= alphabets[fnz(count_alph)]:
        u.append(t.pop())
        if len(t) == 0:
            break
u = u + t[::-1]
ans = ""
for i in u:
    ans += i
print(ans)