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.util.Arrays;
import java.util.Scanner;
import java.util.Stack;

public class CandidateCode {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int arr[] = new int[26];
        String s = sc.next();
        for (int i = 0; i < s.length(); i++) {
            arr[s.charAt(i) - 'a']++;
        }
        Stack<Character> st = new Stack<>();
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            boolean backCheck = false;
//            System.out.println(backCheck+" "+s.charAt(i));
            st.push(s.charAt(i));
            arr[s.charAt(i)-'a']--;
            for (int j = s.charAt(i) - 'a' - 1; j >= 0; j--) {
                if (arr[j] > 0) {
                    backCheck = true;
                    break;
                }
            }
            while (!st.isEmpty() && !backCheck) {
                char popped = st.pop();
//                System.out.println(popped);
                sb.append(popped);
                if (!st.isEmpty()) {
                    backCheck = false;
                    for (int j = st.peek() - 'a' - 1; j >= 0; j--) {
                        if (arr[j] > 0) {
                            backCheck = true;
                            break;
                        }
                    }
                }
            }
        }
        while (!st.isEmpty()) {
            sb.append(st.pop());
        }
        System.out.println(sb);
    }
}
