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.math.BigInteger;
import java.util.*;


public class Main {
    public static void main(String[] args) {
        FastReader scr = new FastReader();
        OutputStream outputStream = System.out;
        PrintWriter out = new PrintWriter(outputStream);

//        int t = scr.nextInt();
//        while (t-- > 0)
        solve(scr, out);
        out.close();
    }


    static void solve(FastReader scr, PrintWriter out) {
        String str = scr.next();

        Deque<Character> t = new LinkedList<>();
        Deque<Character> s = new LinkedList<>();
        StringBuilder u = new StringBuilder("");
        int[] a = new int[26];

        for (int i = str.length() - 1; i > -1; i--) {
            s.push(str.charAt(i));
            a[str.charAt(i) - 'a']++;
        }


        while (!s.isEmpty()) {
            for (int j = 0; j < 26; ) {
                if (a[j] == 0) j++;
                else {
                    while (!t.isEmpty() && !s.isEmpty() && t.peek() <= (char) (j + 'a')) {
                        u.append(t.pop());
                    }
                    if (!s.isEmpty() && (char) (j + 'a') == s.peek()) {
                        u.append(s.pop());
                        a[j]--;
                    } else if (!s.isEmpty() && (char) (j + 'a') != s.peek()) {
                        int te = s.peek() - 'a';
                        t.push(s.pop());
                        a[te]--;
                    }
                }
            }
        }

        while (!t.isEmpty()) {
            u.append(t.pop());
        }
        out.println(u);
    }


    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader() {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }

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

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

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

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

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }
}

