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 Solution
{
       public static void main(String []args)
       {
              Scanner sc = new Scanner(System.in);
              String str = sc.nextLine();
              Stack<Character> st = new Stack<Character>();
              StringBuffer ans = new StringBuffer("");
              int count[] = new int[26];
              int n = str.length();
              for(int i = 0 ; i < n ; i++)
              {
                     count[str.charAt(i)-'a']++;
              }
              int i = 0, j = 0;
              while(true)
              {
                     while(count[j] == 0)
                     {
                     j++;
                     }
                     while(!st.empty() && st.peek() <= (j+97))
                     {
                            ans.append(st.pop());
                     }
                     while(count[j] > 0)
                     {
                            if(str.charAt(i) == (j+97))
                            {
                                   ans.append(str.charAt(i));
                            }
                            
                            else
                            {
                                   st.push(str.charAt(i));
                            }
                            count[str.charAt(i) - 'a']--;
                            i++;
                     }
                     if(i==n)
                     break;
              }
              while(!st.empty())
              {
                     ans.append(st.pop());
              }
              System.out.println(ans);
       }
}