source_code: import java.io.OutputStream;
  import java.io.IOException;
  import java.io.PrintWriter;
  import java.util.Arrays;
  import java.util.InputMismatchException;
  import java.io.Writer;
  import java.io.InputStream;
  
  /**
   * Built using CHelper plug-in
   * Actual solution is at the top
   * @author emotionalBlind
   */
  public class Main {
  	public static void main(String[] args) {
  		InputStream inputStream = System.in;
  		OutputStream outputStream = System.out;
  		InputReader in = new InputReader(inputStream);
  		OutputWriter out = new OutputWriter(outputStream);
  		TaskD solver = new TaskD();
  		solver.solve(1, in, out);
  		out.close();
  	}
  }
  
  class TaskD {
      int[] lo;
      int[] hi;
  
      long[][][][][] dp;
      long[] posVal;
  
      long go(int pos, int isAGreaterLo, int isALessHi, int isBGreaterLo, int isBLessHi) {
          if (pos == 63) {
              return 0;
          }
          if (dp[pos][isAGreaterLo][isALessHi][isBGreaterLo][isBLessHi] != -1) {
              return dp[pos][isAGreaterLo][isALessHi][isBGreaterLo][isBLessHi];
          }
          // range a
          int ua = 0;
          int va = 1;
          if (isALessHi == 0 && hi[pos] == 0) {
              va = 0;
          }
          if (isAGreaterLo == 0 && lo[pos] == 1) {
              ua = 1;
          }
          // range b;
          int ub = 0;
          int vb = 1;
          if (isBLessHi == 0 && hi[pos] == 0) {
              vb = 0;
          }
          if (isBGreaterLo == 0 && lo[pos] == 1) {
              ub = 1;
          }
          long res = 0;
          dp[pos][isAGreaterLo][isALessHi][isBGreaterLo][isBLessHi] = 0;
          for (int i = ua; i <= va; ++i) {
              int newIsAGreaterLo = isAGreaterLo;
              int newIsALessHi = isALessHi;
              if (i < hi[pos]) newIsALessHi = 1;
              if (i > lo[pos]) newIsAGreaterLo = 1;
              for (int j = ub; j <= vb; ++j) {
                  int newIsBGreaterLo = isBGreaterLo;
                  int newIsBLessHi = isBLessHi;
                  if (j < hi[pos]) newIsBLessHi = 1;
                  if (j > lo[pos]) newIsBGreaterLo = 1;
                  long val = 0;
                  if (i != j) val = posVal[pos];
                  val += go(pos + 1, newIsAGreaterLo, newIsALessHi, newIsBGreaterLo, newIsBLessHi);
                  res = Math.max(res, val);
              }
          }
          dp[pos][isAGreaterLo][isALessHi][isBGreaterLo][isBLessHi] = res;
          return res;
      }
  
      public void solve(int testNumber, InputReader in, OutputWriter out) {
          lo = new int[63];
          hi = new int[63];
          long a = in.readLong();
          long b = in.readLong();
          Binary.convertBinary(a, lo);
          Binary.convertBinary(b, hi);
          posVal = new long[63];
          posVal[62] = 1;
          for (int i = 61; i >= 0; --i) {
              posVal[i] = posVal[i + 1] * 2;
          }
          dp = new long[65][2][2][2][2];
          for (long[][][][] a1 : dp) {
              for (long[][][] a2 : a1) {
                  for (long[][] a3 : a2) {
                      for (long[] a4 : a3) {
                          Arrays.fill(a4, -1);
                      }
                  }
              }
          }
          long res = go(0, 0, 0, 0, 0);
          out.printLine(res);
      }
  }
  
  class InputReader {
  
      private InputStream stream;
      private byte[] buf = new byte[1024];
      private int curChar;
      private int numChars;
  
      public InputReader(InputStream stream) {
          this.stream = stream;
      }
  
      public int read() {
          // InputMismatchException -> UnknownError
          if (numChars == -1)
              throw new UnknownError();
          if (curChar >= numChars) {
              curChar = 0;
              try {
                  numChars = stream.read(buf);
              } catch (IOException e) {
                  throw new UnknownError();
              }
              if (numChars <= 0)
                  return -1;
          }
          return buf[curChar++];
      }
  
      public long readLong() {
          int c = read();
          while (isSpaceChar(c))
              c = read();
          int sgn = 1;
          if (c == '-') {
              sgn = -1;
              c = read();
          }
          long res = 0;
          do {
              if (c < '0' || c > '9')
                  throw new InputMismatchException();
              res *= 10;
              res += c - '0';
              c = read();
          } while (!isSpaceChar(c));
          return res * sgn;
      }
  
      public static boolean isSpaceChar(int c) {
          return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
      }
  
      }
  
  class OutputWriter {
      private final PrintWriter writer;
  
      public OutputWriter(OutputStream outputStream) {
          writer = new PrintWriter(outputStream);
      }
  
      public OutputWriter(Writer writer) {
          this.writer = new PrintWriter(writer);
      }
  
      public void print(Object...objects) {
          for (int i = 0; i < objects.length; i++) {
              if (i != 0)
                  writer.print(' ');
              writer.print(objects[i]);
          }
      }
  
      public void printLine(Object...objects) {
          print(objects);
          writer.println();
      }
  
      public void close() {
          writer.close();
      }
  
  }
  
  class Binary {
      public static void convertBinary(long val, int[] a) {
          int last = a.length - 1;
          Arrays.fill(a, 0);
          while (val > 0) {
              a[last] = (int) (val % 2);
              last--;
              val /= 2;
          }
      }
  }
  
  