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
restantes = {}

def possui_menor(l):
  n = ord(l) - ord('a')
  for k in sorted(restantes.keys()):
    if k >= l: break
    if restantes[k] > 0:
      return True
  return False

s = list(input())
pilha = []
resposta = ""

for l in s:
  if l not in restantes:
    restantes[l] = 0
  restantes[l] += 1

for l in s:
  pilha.append(l)
  restantes[l] = restantes[l] - 1
  prox = pilha[-1]
  while len(pilha) > 0 and (not (possui_menor(prox))):
    resposta += pilha.pop(-1)
    if len(pilha) > 0:
        prox = pilha[-1]    
  
while len(pilha) > 0:
  resposta += pilha.pop(-1)

print(resposta)