#include<stdio.h>
int main()
{
	long long int a, b;
	scanf("%lld %lld", &a, &b);
	if (a > b)
	{
		a ^= b;
		b ^= a;
		a ^= b;
	}
	long long int aa, bb;
	for (aa = 1; aa <= a; aa *= 2);
	aa /= 2;
	for (bb = 1; bb <= b; bb *= 2);
	bb /= 2;
	if (aa < bb)
		printf("%lld\n", a);
	else
		printf("%lld\n", aa - 1);
	return 0;
}