Once again Tavas started eating coffee mix without water! Keione told him that it smells awful, but he didn't stop doing that. That's why Keione told his smart friend, SaDDas to punish him! SaDDas took Tavas' headphones and told him: "If you solve the following problem, I'll return it to you."

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The problem is: 

You are given a lucky number n. Lucky numbers are the positive integers whose decimal representations contain only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not.

If we sort all lucky numbers in increasing order, what's the 1-based index of n? 

Tavas is not as smart as SaDDas, so he asked you to do him a favor and solve this problem so he can have his headphones back.

Input

The first and only line of input contains a lucky number n (1 ≤ n ≤ 109).

Output

Print the index of n among all lucky numbers.

Examples

Input

4


Output

1


Input

7


Output

2


Input

77


Output

6
import java.io.*;
import java.util.StringTokenizer;
import java.util.*;

/**
 * Created by gouthamvidyapradhan on 30/06/2020
 */
public class TavasAndSaDDas {
    private static PrintWriter pw = new PrintWriter(new BufferedOutputStream(System.out, 500000));
    static class MyScanner {
        /**
         * Buffered reader
         */
        private static BufferedReader br = new BufferedReader(
                new InputStreamReader(System.in));

        private static StringTokenizer st;

        /**
         * Read integer
         *
         * @return
         * @throws Exception
         */
        public static int readInt() throws Exception {
            try {
                if (st != null && st.hasMoreTokens()) {
                    return parseInt(st.nextToken());
                }
                String str = br.readLine();
                if(str == null) return -2;
                if (!str.trim().equals("")) {
                    st = new StringTokenizer(str);
                    return parseInt(st.nextToken());
                }
            } catch (IOException e) {
                close();
                return -1;
            }
            return -1;
        }

        /**
         * Read integer
         *
         * @return
         * @throws Exception
         */
        public static long readLong() throws Exception {
            try {
                if (st != null && st.hasMoreTokens()) {
                    return Long.parseLong(st.nextToken());
                }
                String str = br.readLine();
                if (str != null && !str.trim().equals("")) {
                    st = new StringTokenizer(str);
                    return Long.parseLong(st.nextToken());
                }
            } catch (IOException e) {
                close();
                return -1;
            }
            return -1;
        }

        /**
         * Read line
         * @return
         * @throws Exception
         */
        public static String readLine() throws Exception
        {
            return br.readLine();
        }

        /**
         * Parse to integer
         * @param in
         * @return integer value
         */
        public static int parseInt(String in)
        {
            // Check for a sign.
            int num  = 0, sign = -1, i = 0;
            final int len  = in.length( );
            final char ch  = in.charAt( 0 );
            if ( ch == '-' )
                sign = 1;
            else
                num = '0' - ch;

            // Build the number.
            i+=1;
            while ( i < len )
                num = num*10 + '0' - in.charAt( i++ );
            return sign * num;
        }

        /**
         * Close BufferedReader
         *
         * @throws Exception
         */
        public static void close() throws Exception {
            br.close();
        }
    }

    public static void main(String[] args) throws Exception{
        int n = MyScanner.readInt();
        List<String> list = new ArrayList<>();
        list.add("");
        int i = 0;
        boolean found = false;
        while(true){
            List<String> temp = new ArrayList<>();
            for(String s : list){
                String num1 = 4 + s;
                temp.add(num1);
                i++;
                if(Long.parseLong(num1) == n){
                    found = true;
                    pw.println(i);
                    break;
                }
            }
            if(found) break;
            for(String s : list){
                String num1 = 7 + s;
                temp.add(num1);
                i++;
                if(Long.parseLong(num1) == n){
                    found = true;
                    pw.println(i);
                    break;
                }
            }
            list = temp;
            if(found) break;
        }
        pw.flush();
        pw.close();
    }
}
