source_code: 
  // @author Sanzhar
  import java.io.*;
  import java.util.*;
  import java.awt.Point;
  
  public class Template {
  
      BufferedReader in;
      PrintWriter out;
      StringTokenizer st;
  
      String next() {
          while (st == null || !st.hasMoreTokens()) {
              try {
                  st = new StringTokenizer(in.readLine());
              } catch (Exception e) {
              }
          }
          return st.nextToken();
      }
  
      int nextInt() {
          return Integer.parseInt(next());
      }
  
      long nextLong() {
          return Long.parseLong(next());
      }
  
      double nextDouble() {
          return Double.parseDouble(next());
      }
  
      public void run() throws Exception {
          //in = new BufferedReader(new FileReader("input.txt"));
          //out = new PrintWriter(new FileWriter("output.txt"));
          in = new BufferedReader(new InputStreamReader(System.in));
          out = new PrintWriter(System.out);
          solve();
          out.flush();
          out.close();
          in.close();
      }
  
      public void solve() throws Exception {
          long l = nextLong();
          long r = nextLong();
          long[] x = new long[100];
          int kx = 0;
          while (r > 0) {
              x[kx++] = r % 2;
              r /= 2;
          }
          long[] y = new long[100];
          int ky = 0;
          while (l > 0) {
              y[ky++] = l % 2;
              l /= 2;
          }
          long[] ans = new long[100];
          boolean ok = false;
          for (int k = kx - 1; k >= 0; k--) {
              if (ok) {
                  ans[k] = 1;
                  continue;
              }
              if (x[k] > y[k]) {
                  ans[k] = 1;
                  ok = true;
              }
          }
          long a = 0;
          long p2 = 1;
          for (int i = 0; i < kx; i++) {
              a += p2 * ans[i];
              p2 *= 2;
          }
          out.println(a);
      }
  
      public static void main(String[] args) throws Exception {
          new Template().run();
      }
  }
  