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
import bisect
from itertools import accumulate
import os
import sys
import math
from decimal import *
from io import BytesIO, IOBase
 
BUFSIZE = 8192
 
 
class FastIO(IOBase):
    newlines = 0
 
    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None
 
    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()
 
    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()
 
    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)
 
 
class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")
 
 
sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
 
 
def input(): return sys.stdin.readline().rstrip("\r\n")
def isPrime(n) :
    if (n <= 1) : return False
    if (n <= 3) : return True
    if (n % 2 == 0 or n % 3 == 0) : return False
    i = 5
    while(i * i <= n) :
        if (n % i == 0 or n % (i + 2) == 0) :
            return False
        i = i + 6
    return True
def SieveOfEratosthenes(n): 
    prime=[]
    primes = [True for i in range(n+1)] 
    p = 2
    while (p * p <= n): 
          
        if (primes[p] == True): 
            prime.append(p)
            for i in range(p * p, n+1, p): 
                primes[i] = False
        p += 1
    return prime
def primefactors(n):
    fac=[]
    while(n%2==0):
        fac.append(2)
        n=n//2
    for i in range(3,int(math.sqrt(n))+2):
        while(n%i==0):
            fac.append(i)
            n=n//i
    if n>1:
        fac.append(n)
    return fac
def factors(n):
    fac=set()
    fac.add(1)
    fac.add(n)
    for i in range(2,int(math.sqrt(n))+1):
        if n%i==0:
            fac.add(i)
            fac.add(n//i)
    return list(fac)
def modInverse(a, m):
    m0 = m
    y = 0
    x = 1
    if (m == 1):
        return 0
    while (a > 1):
        q = a // m
        t = m
        m = a % m
        a = t
        t = y
        y = x - q * y
        x = t
    if (x < 0):
        x = x + m0
    return x
#------------------------------------------------------code by AD18/apurva3455
s=input()
a=[0]*26
for i in range(0,len(s)):
    a[ord(s[i])-97]+=1
t=[]
stack=[]
ans=""
for i in s:
    t.append(i)
    a[ord(i)-97]-=1
    while t and sum(a[:ord(t[-1])-97])==0:
        ans+=t.pop()
print(ans)
        
    