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 fn(temp, count):
    index = ord(temp) - 97 -1
    while(index >= 0):
        if(count[index]>0):
            return False
        index -= 1
    return True

s = raw_input()
count = [0]*26
for i in s:
    count[ord(i)-97] += 1
t = []
u = []
for i in s:
    t.append(i)
    count[ord(t[-1])-97] -= 1
    while(t and fn(t[-1], count)):
        u.append(t.pop())
while t:
    u.append(t.pop())
print ''.join(u)