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
//package main;

import java.io.*;
import java.util.*;
import java.math.*;

public final class Main {
    BufferedReader br;
    StringTokenizer stk;
    
    public static void main(String[] args) throws Exception {
        new Main().run();
    }
    
    {
        stk = null;
        br = new BufferedReader(new InputStreamReader(System.in));
    }
    
    long mod = 1000_000_000 + 7;
    StringBuilder res = new StringBuilder(1000005);
    void run() throws Exception {
        char[] c = nc();
        Stack<Character> stack = new Stack<>();
        int[] counts = new int[26];
        for(char ch : c) {
            counts[ch - 'a']++;
        }
        
        for(int i = 0; i < c.length; i++) {
            stack.push(c[i]);
            counts[c[i] - 'a']--;
            while(!stack.isEmpty() && stack.peek() <= findMin(counts)) {
                res.append(stack.pop());
            }
        }
        
        while(!stack.isEmpty()) {
            res.append(stack.pop());
        }
        
        System.out.println(res);
    }
    
    char findMin(int[] a) {
        int value = 'a';
        for(int i = 0; i < a.length; i++) {
            if(a[i] > 0) {
                value = (i + 'a');
                break;
            }
        }
        return (char) value;
    }
    
    //Reader & Writer
    String nt() throws Exception {
        if (stk == null || !stk.hasMoreTokens())
            stk = new StringTokenizer(br.readLine(), " ");
        return stk.nextToken();
    }

    char[] nc() throws Exception {
        return nt().toCharArray();
    }

    int ni() throws Exception {
        return Integer.parseInt(nt());
    }

    long nl() throws Exception {
        return Long.parseLong(nt());
    }
    
    double nd() throws Exception {
        return Double.parseDouble(nt());
    }
    
    //Some Misc methods
    long get(int l, int r, long[] a) {
        return l == 0 ? a[r] : a[r] - a[l - 1];
    }
    
    void shuffle(long[] a) {
        Random r = new Random();
        for(int i = 0; i < a.length; i++) {
            int idx = r.nextInt(a.length);
            long temp = a[i];
            a[i] = a[idx];
            a[idx] = temp;
        }
    }
    
    void reverse(long[] a) {
        for(int i = 0, j = a.length - 1; i < j; i++, j--) {
            long temp = a[i];
            a[i] = a[j];
            a[j] = temp;
        }
    }
    
    void print(int[] a) {
        System.out.println(Arrays.toString(a));
    }
}