Baekjoon #1052

import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) {
        FastReader rd = new FastReader();

        int N = rd.nextInt();
        int K = rd.nextInt();

        for (int i = N; i <= Integer.MAX_VALUE; i++) {
//            Integer.bitCount를 직접 구현하는 경우
//            int bit = 0;
//            int cnt = 0;
//            while (i >= (1 << bit)) {
//                if ((i & 1 << bit) != 0) {
//                    cnt++;
//                }
//                bit++;
//            }
//
//            if (cnt <= K) {
//                System.out.println(i - N);
//                return;
//            }

            if (Integer.bitCount(i) <= K) {
                System.out.println(i - N);
                return;
            }
        }
        System.out.println(-1);
    }

    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;
        }
    }
}