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.util.*;
import java.lang.*;
import java.io.*;
import java.math.*;
import java.text.*;
public class Prac{     
    static class InputReader { 
        private final InputStream stream;
        private final byte[] buf = new byte[8192];
        private int curChar, snumChars;
        public InputReader(InputStream st) {
            this.stream = st;
        } 
        public int read() {
            if (snumChars == -1)
                throw new InputMismatchException();
            if (curChar >= snumChars) {
                curChar = 0;
                try {
                    snumChars = stream.read(buf);
                } 
                catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (snumChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }
        public int ni() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        } 
        public long nl() {
            int c = read();
            while (isSpaceChar(c)) {
            c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        } 
        public int[] nia(int n) {
            int a[] = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = ni();
            }
            return a;
        } 
        public String rs() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                    c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }
        public String nextLine() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isEndOfLine(c));
            return res.toString();
        } 
        public boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }
 
        private boolean isEndOfLine(int c) {
            return c == '\n' || c == '\r' || c == -1;
        } 
    }
    public static class Key {

        private final int x;
        private final int y;

        public Key(int x, int y) {
            this.x = x;
            this.y = y;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (!(o instanceof Key)) return false;
            Key key = (Key) o;
            return x == key.x && y == key.y;
        }

        @Override
        public int hashCode() {
            int result = x;
            result = 31 * result + y;
            return result;
        }

    }
    
    static PrintWriter w = new PrintWriter(System.out);
    static long mod=998244353L,mod1=1000000007;
    static int co[][];
    static void dsort(){
        Arrays.parallelSort(co,(o1,o2)->o1[0]!=o2[0]?o1[0]-o2[0]:o1[1]-o2[1]);
    }
    static long  power(long x, long y) { 
        long temp=0; 
        if( y == 0) 
            return 1; 
        temp = power(x, y/2); 
        if (y%2 == 0) 
            return (temp*temp)%mod; 
        else
            return (((x*temp)%mod)*temp)%mod; 
    } 
    static long modInverse(long a, long m){
        long num=m;
        long x=1;
        long power=a%mod;
        while(num>0){
              if(num%2==1){
                  x=(x*power)%mod;
            }
            num>>=1;
            power=(power*power)%mod;         
        }
        return x;
    }
    static long fact[]=new long[1000005];
    public static void findFact(){
        fact[0]=1;
        for(int i=1;i<=1000000;i++){
            fact[i]=(i*fact[i-1])%mod;
        }
    } 
    static long nCr(int n,int r){
        return (fact[n]*modInverse((fact[r]*fact[n-r])%mod,mod-2))%mod;
    }
    public static void main (String[] args)throws IOException{
        InputReader sc=new InputReader(System.in);
        String ans[]=new String[10000];
        ans[1]="4";
        ans[2]="7";
        int j=1;
        Queue<String> q=new LinkedList<>();
        q.add("4");
        q.add("7");
        while(true){
            String s=q.poll();
            ans[j++]=s;
            //w.println(s);
            q.add(s+"4");
            q.add(s+"7");
            if(j==10000)break;
        }
        int n=sc.ni();
        for(int i=1;i<10000;i++){
            int x=Integer.parseInt(ans[i]);
            if(x==n){
                w.println(i);
                break;
            }
        }
        w.close();
    }
}