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.*;
public class ms{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.next();
		int[] arr = new int[26];
		for(int i=0;i<s.length();i++){
			arr[s.charAt(i)-'a']++;
		}
		String res="";
		Stack<Character> st = new Stack<Character>();
		StringBuilder sb = new StringBuilder();
		for(int i=0;i<s.length();i++){
			// if(minimal(arr,s.charAt(i))){
			// 	res=res+s.charAt(i);
			// 	arr[s.charAt(i)-'a']--;
			// }
			// else{
			// 	st.push(s.charAt(i));
			// }
			char c = s.charAt(i);
			st.push(c);
			arr[c-'a']--;
			while(!st.isEmpty() && minimal(arr,st.peek())){
				sb.append(st.pop());
			}
		}
		// while(!st.isEmpty()){
		// 	res=res+st.pop();
		// }
		System.out.println(sb);
	}
	public static boolean minimal(int[] arr,char c){
		int p = c-'a';
		//System.out.println(p);
		for(int i=0;i<p;i++){
		//	System.out.println(arr[i]);
			if(arr[i]!=0){
				return false;
			}
		}
		return true;
	}
}