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
//package cf;
import java.io.*;
import java.util.*;

public final class Cf {

    public static void main(String[] args) throws Exception {
        BufferedWriter out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(java.io.FileDescriptor.out), "ASCII"), 512);        
        FastReader sc = new FastReader();
        char c[]=sc.next().toCharArray();
        ArrayList<Character>ans=new ArrayList<>();
        Stack<Character>stack=new Stack();
        int d[]=new int[c.length];
        d[c.length-1]=c[c.length-1]-'a';
        for(int i=c.length-2;i>=0;i--)d[i]=Math.min(d[i+1], c[i]-'a');
      //  for(int v:d)System.out.print((char)(v+'a')+" ");
       // System.out.println();
        for(int i=0;i<c.length;i++)
        {
            while(!stack.isEmpty()&&stack.peek()<=(char)(d[i]+'a')){ans.add(stack.pop());}
            stack.add(c[i]);
          //  debug(stack+" stack "+ans+" ans is ");
        }
        while(!stack.isEmpty())ans.add(stack.pop());
        for(char ch:ans)out.write(ch+"");
        out.flush();
        
    }
    public static void debug(String s)
    {
        System.out.println(s);
    }

    ///////////////////////////////////////////////////////////////////////////////////
    //////////////////////////////////////////////////////////////////////////////////////////////
    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;            
        }        
    }
    //////////////////////////////////////////////////////////////////

    static class Reader {        

        final private int BUFFER_SIZE = 1 << 16;        
        private DataInputStream din;        
        private byte[] buffer;        
        private int bufferPointer, bytesRead;        
        
        public Reader() {            
            din = new DataInputStream(System.in);            
            buffer = new byte[BUFFER_SIZE];            
            bufferPointer = bytesRead = 0;            
        }        
        
        public Reader(String file_name) throws IOException {            
            din = new DataInputStream(new FileInputStream(file_name));            
            buffer = new byte[BUFFER_SIZE];            
            bufferPointer = bytesRead = 0;            
        }        
        
        public String readLine() throws IOException {            
            byte[] buf = new byte[1002]; // line length 
            int cnt = 0, c;            
            while ((c = read()) != -1) {                
                if (c == '\n') {
                    break;
                }                
                buf[cnt++] = (byte) c;                
            }            
            return new String(buf, 0, cnt);            
        }        
        
        public int nextInt() throws IOException {            
            int ret = 0;            
            byte c = read();            
            while (c <= ' ') {
                c = read();
            }            
            boolean neg = (c == '-');            
            if (neg) {
                c = read();
            }            
            do {                
                ret = ret * 10 + c - '0';                
            } while ((c = read()) >= '0' && c <= '9');            
            
            if (neg) {
                return -ret;
            }            
            return ret;            
        }        
        
        public long nextLong() throws IOException {            
            long ret = 0;            
            byte c = read();            
            while (c <= ' ') {
                c = read();
            }            
            boolean neg = (c == '-');            
            if (neg) {
                c = read();
            }            
            do {                
                ret = ret * 10 + c - '0';                
            } while ((c = read()) >= '0' && c <= '9');            
            if (neg) {
                return -ret;
            }            
            return ret;            
        }        
        
        public double nextDouble() throws IOException {            
            double ret = 0, div = 1;            
            byte c = read();            
            while (c <= ' ') {
                c = read();
            }            
            boolean neg = (c == '-');            
            if (neg) {
                c = read();
            }            
            
            do {                
                ret = ret * 10 + c - '0';                
            } while ((c = read()) >= '0' && c <= '9');            
            
            if (c == '.') {                
                while ((c = read()) >= '0' && c <= '9') {                    
                    ret += (c - '0') / (div *= 10);                    
                }                
            }            
            
            if (neg) {
                return -ret;
            }            
            return ret;            
        }        
        
        private void fillBuffer() throws IOException {            
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE);            
            if (bytesRead == -1) {
                buffer[0] = -1;
            }            
        }        
        
        private byte read() throws IOException {            
            if (bufferPointer == bytesRead) {
                fillBuffer();
            }            
            return buffer[bufferPointer++];            
        }        
        
        public void close() throws IOException {            
            if (din == null) {
                return;
            }            
            din.close();            
        }        
    }    
}
