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.Stack;
import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStreamReader; 
import java.util.StringTokenizer; 
public class Main {

	public static void main(String[] args) {
		FastReader obj = new FastReader();
		String s = obj.next();
		Stack<Character> stack = new Stack<>();
		int[] count = new int[26];
		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);
	}
	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; 
        } 
    } 
}
