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.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Stack;
import java.util.StringTokenizer;

public class ecf19C {
    public static void main(String[] args) {
        FastReader reader = new FastReader();
        String s = reader.next();
        String minS = getMinChars(s);
        StringBuffer res = new StringBuffer();
        Stack<Character> stack = new Stack<>();
        for (int i = 0; i < s.length(); i++) {
            if (stack.empty()) {
                stack.push(s.charAt(i));
            } else {
                while (!stack.empty() && stack.peek() <= minS.charAt(i)) {
                    res.append(stack.pop());
                }
                stack.push(s.charAt(i));
            }
        }
        while (!stack.empty()) {
            res.append(stack.pop());
        }
        System.out.println(res.toString());
    }

    static String getMinChars(String s) {
        StringBuffer res = new StringBuffer();
        char curMin = 'z';
        for (int i = s.length() - 1; i >= 0; i--) {
            if (s.charAt(i) < curMin) {
                curMin = s.charAt(i);
            }
            res.append(curMin);
        }
        return res.reverse().toString();
    }

    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;
        }
    }
}

