Package for this problem was not updated by the problem writer or Codeforces administration after we’ve upgraded the judging servers. To adjust the time limit constraint, solution execution time will be multiplied by 2. For example, if your solution works for 400 ms on judging servers, then value 800 ms will be displayed and used to determine the verdict.

Virtual contest is a way to take part in past contest, as close as possible to participation on time. It is supported only ACM-ICPC mode for virtual contests.
If you've seen these problems, a virtual contest is not for you - solve these problems in the archive.
If you just want to solve some problem from a contest, a virtual contest is not for you - solve this problem in the archive.
Never use someone else's code, read the tutorials or communicate with other person during a virtual contest.

No tag edit access

D. Little Girl and Maximum XOR

time limit per test

2 secondsmemory limit per test

256 megabytesinput

standard inputoutput

standard outputA little girl loves problems on bitwise operations very much. Here's one of them.

You are given two integers *l* and *r*. Let's consider the values of for all pairs of integers *a* and *b* (*l* ≤ *a* ≤ *b* ≤ *r*). Your task is to find the maximum value among all considered ones.

Expression means applying bitwise excluding or operation to integers *x* and *y*. The given operation exists in all modern programming languages, for example, in languages *C*++ and *Java* it is represented as "^", in *Pascal* — as «xor».

Input

The single line contains space-separated integers *l* and *r* (1 ≤ *l* ≤ *r* ≤ 10^{18}).

Please, do not use the %lld specifier to read or write 64-bit integers in С++. It is preferred to use the cin, cout streams or the %I64d specifier.

Output

In a single line print a single integer — the maximum value of for all pairs of integers *a*, *b* (*l* ≤ *a* ≤ *b* ≤ *r*).

Examples

Input

1 2

Output

3

Input

8 16

Output

31

Input

1 1

Output

0

Codeforces (c) Copyright 2010-2017 Mike Mirzayanov

The only programming contests Web 2.0 platform

Server time: Jun/29/2017 01:31:50 (p1).

Desktop version, switch to mobile version.
User lists

Name |
---|