#include <iostream>
#include <algorithm>
using namespace std;

int main() {
	int a, b;
	cin >> a >> b;
	if (a > b) { swap(a, b); }

	int ka, kb;
	for (ka = 29; ka >= 0; ka--) if ((a >> ka) & 1) break;
	for (kb = 29; kb >= 0; kb--) if ((b >> kb) & 1) break;
	
	if (ka < kb) { cout << a << endl; return 0; }
	cout << (1LL << ka) - 1 << endl;
	return 0;
}