import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Collections;
import java.util.NoSuchElementException;

public class Main {
    static FastScanner scan = new FastScanner();

    public static void main(String[] args) {
        int N = scan.nextInt();
        int K = scan.nextInt();
        
        ArrayList<Integer> left = new ArrayList<>();
        ArrayList<Integer> right = new ArrayList<>();
        int count = 0;
        
        for(int i=1; i<Math.pow(2,N)-1; i++) {
            int tmp = i;
            left.clear();
            right.clear();
            
            for(int j=1; j<=N; j++) {
                if((tmp & 0x1) == 0) {
                    left.add(j);
                } else {
                    right.add(j);
                }
                tmp >>= 1;
            }
            Collections.sort(left);
            if(left.get(0) != K) continue;
            Collections.sort(right);
            if(left.get(left.size()-1) > right.get(0)) {
                count ++;
            }
        }
        System.out.println(count);
    }
    
    static class FastScanner {
        private final InputStream in = System.in;
        private final byte[] buffer = new byte[1024];
        private int ptr = 0;
        private int buflen = 0;

        private boolean hasNextByte() {
            if (ptr < buflen) {
                return true;
            } else {
                ptr = 0;
                try {
                    buflen = in.read(buffer);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                if (buflen <= 0) {
                    return false;
                }
            }
            return true;
        }

        private int readByte() {
            if (hasNextByte())
                return buffer[ptr++];
            else
                return -1;
        }

        private static boolean isPrintableChar(int c) {
            return 33 <= c && c <= 126;
        }

        private void skipUnprintable() {
            while (hasNextByte() && !isPrintableChar(buffer[ptr]))
                ptr++;
        }

        public boolean hasNext() {
            skipUnprintable();
            return hasNextByte();
        }

        public String next() {
            if (!hasNext())
                throw new NoSuchElementException();
            StringBuilder sb = new StringBuilder();
            int b = readByte();
            while (isPrintableChar(b)) {
                sb.appendCodePoint(b);
                b = readByte();
            }
            return sb.toString();
        }

        public int nextInt() {
            return (int) nextLong();
        }

        public long nextLong() {
            if (!hasNext())
                throw new NoSuchElementException();
            long n = 0;
            boolean minus = false;
            int b = readByte();
            if (b == '-') {
                minus = true;
                b = readByte();
            }
            if (b < '0' || '9' < b) {
                throw new NumberFormatException();
            }
            while (true) {
                if ('0' <= b && b <= '9') {
                    n *= 10;
                    n += b - '0';
                } else if (b == -1 || !isPrintableChar(b)) {
                    return minus ? -n : n;
                } else {
                    throw new NumberFormatException();
                }
                b = readByte();
            }
        }
    }
}