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.Scanner;
import java.util.Stack;

public class Main {

	public static void main(String[] args) {
		Scanner obj = new Scanner(System.in);
		String s = obj.next();
		Stack<Character> stack = new Stack<>();
		int[] count = new int[26];
		obj.close();
		for(int i=0;i<s.length();i++) {
			count[s.charAt(i)-'a']++;
		}
		StringBuilder ans = new StringBuilder();
		int i=0;
		for(char ch = 'a';ch<='z';ch++) {
			while(!stack.empty() && stack.peek()<=ch) {
				ans.append(stack.pop());
			}
			int pos = s.indexOf(ch, i);
			while(pos>=0) {
				while(i<pos) {
					stack.push(s.charAt(i));
					i++;
				}
				ans.append(ch);
				i++;
				pos=s.indexOf(ch, i);
			}
		}
		System.out.print(ans);
	}
}
