One beautiful July morning a terrible thing happened in Mainframe: a mean virus Megabyte somehow got access to the memory of his not less mean sister Hexadecimal. He loaded there a huge amount of n different natural numbers from 1 to n to obtain total control over her energy.

But his plan failed. The reason for this was very simple: Hexadecimal didn't perceive any information, apart from numbers written in binary format. This means that if a number in a decimal representation contained characters apart from 0 and 1, it was not stored in the memory. Now Megabyte wants to know, how many numbers were loaded successfully.

Input

Input data contains the only number n (1 ≤ n ≤ 109).

Output

Output the only number — answer to the problem.

Examples

Input

10


Output

2

Note

For n = 10 the answer includes numbers 1 and 10.
/*
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 * and open the template in the editor.
 */

/**
 *
 * @author dipankar12
 */
import java.io.*;
import java.util.*;
public class r9c {
    public static void main(String args[])
    {
        fastio in=new fastio(System.in);
        PrintWriter pw=new PrintWriter(System.out);

        int n=in.nextInt();
        int len=(n+"").length();
        
        ArrayList<Integer> al=new ArrayList<Integer>();
        al.add(1);
        int count=0;
        while(al.size()!=0)
        {
            if(al.size()==0)
                break;
            int x=al.get(0);
            al.remove(0);
            //pw.println(x);
            count++;
            int y=x*10;
            if(y<=n)
                al.add(y);
            y=x*10+1;
            if(y<=n)
                al.add(y);
        }
        
        pw.println(count);
        pw.close();
    }

    static class fastio {
     
            private final InputStream stream;
            private final byte[] buf = new byte[8192];
            private int cchar, snchar;
            private SpaceCharFilter filter;
     
            public fastio(InputStream stream) {
                this.stream = stream;
            }
     
            public int nxt() {
                if (snchar == -1)
                    throw new InputMismatchException();
                if (cchar >= snchar) {
                    cchar = 0;
                    try {
                        snchar = stream.read(buf);
                    } catch (IOException e) {
                        throw new InputMismatchException();
                    }
                    if (snchar <= 0)
                        return -1;
                }
                return buf[cchar++];
            }
     
            public int nextInt() {
                int c = nxt();
                while (isSpaceChar(c)) {
                    c = nxt();
                }
                int sgn = 1;
                if (c == '-') {
                    sgn = -1;
                    c = nxt();
                }
                int res = 0;
                do {
                    if (c < '0' || c > '9')
                        throw new InputMismatchException();
                    res *= 10;
                    res += c - '0';
                    c = nxt();
                } while (!isSpaceChar(c));
                return res * sgn;
            }
     
            public long nextLong() {
                int c = nxt();
                while (isSpaceChar(c)) {
                    c = nxt();
                }
                int sgn = 1;
                if (c == '-') {
                    sgn = -1;
                    c = nxt();
                }
                long res = 0;
                do {
                    if (c < '0' || c > '9')
                        throw new InputMismatchException();
                    res *= 10;
                    res += c - '0';
                    c = nxt();
                } while (!isSpaceChar(c));
                return res * sgn;
            }
     
            public int[] nextIntArray(int n) {
                int a[] = new int[n];
                for (int i = 0; i < n; i++) {
                    a[i] = nextInt();
                }
                return a;
            }
     
            public String readString() {
                int c = nxt();
                while (isSpaceChar(c)) {
                    c = nxt();
                }
                StringBuilder res = new StringBuilder();
                do {
                    res.appendCodePoint(c);
                    c = nxt();
                } while (!isSpaceChar(c));
                return res.toString();
            }
     
            public String nextLine() {
                int c = nxt();
                while (isSpaceChar(c))
                    c = nxt();
                StringBuilder res = new StringBuilder();
                do {
                    res.appendCodePoint(c);
                    c = nxt();
                } while (!isEndOfLine(c));
                return res.toString();
            }
     
            public boolean isSpaceChar(int c) {
                if (filter != null)
                    return filter.isSpaceChar(c);
                return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
            }
     
            private boolean isEndOfLine(int c) {
                return c == '\n' || c == '\r' || c == -1;
            }
     
            public interface SpaceCharFilter {
                public boolean isSpaceChar(int ch);
            }
        }
    

}
