#include <bits/stdc++.h>
using namespace std;

long long a, b, u = 1, v = 1;

int main()
{
	cin >> a >> b;

	if (a > b)
		swap(a, b);

	while (u * 2 <= b)
		u *= 2;

	while (v * 2 <= a)
		v *= 2;

	if (u > v)
		cout << a << endl;
	else
		cout << v - 1 << endl;
}