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

public class code {
    static Reader sc = new Reader();
    static PrintWriter out = new PrintWriter(System.out);

    public static void main(String[] args) {
        char[] s = sc.next().toCharArray();
        int[] freq = new int[26];
        for (char c : s) {
            freq[c - 'a']++;
        }
        Stack<Character> st = new Stack<>();
        StringBuilder ans = new StringBuilder();
        for (char c : s) {
            char getMin = '$';
            for (int j = 0; j < 26; j++) {
                if (freq[j] > 0) {
                    getMin = (char) ('a' + j);
                    break;
                }
            }
            while (!st.isEmpty() && st.peek() <= getMin) {
                ans.append(st.pop());
            }
            st.push(c);
            freq[c - 'a']--;
        }
        while (!st.isEmpty()) {
            ans.append(st.pop());
        }
        out.println(ans);
        out.close();
    }

    static class Reader {
        BufferedReader br;
        StringTokenizer st;

        Reader() {
            br = new BufferedReader(new InputStreamReader(System.in));
            st = new StringTokenizer("");
        }

        Reader(File f) throws FileNotFoundException {
            br = new BufferedReader(new FileReader(f));
            st = new StringTokenizer("");
        }

        String next() {
            while (!st.hasMoreTokens())
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }

        double nextDouble() {
            return Double.parseDouble(next());
        }
    }
}