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 getindex(a):
    return ord(a)-97

s = input()  #input string
cs = [0 for i in range(26)] # count of chars in ascending order like cs[0] represents count of a in string
t = [] #stack t
u = [] #stack u

for i in s:
    cs[getindex(i)]+=1
    
ls = 0 
for i in range(len(s)):
    si = getindex(s[i])
    #print(cs)
    while cs[ls]==0:
        ls+=1
    while t and getindex(t[-1])<=ls:
        u.append(t.pop())
    if ls!=si:
        t.append(s[i])
        #print(t)
    else:
        u.append(s[i])
    cs[si]-=1
while t:
    u.append(t.pop())
print("".join(u))
