#include <bits/stdc++.h>
using namespace std;
bool isPowerofTwo(int n) {
    
    // Check if n is positive and n & ~(n-1) equals n
    return (n > 0) && ((n & (~(n-1))) == n);
}

int main() {
    long long int a,c;
    cin >> a >>c;
    if(a>c) swap(a,c);
    long long int val = log2(c);
    long long int ans = 1;
    if(isPowerofTwo(a) && isPowerofTwo(c)) ans++;
    ans = ans << val;
    cout << ans-1;
    
	// your code goes here

}