#include <cstdio>
#include <vector>
#include <algorithm>
#include <functional>
using namespace std;

int main() {
    int a, b;
    scanf("%d%d", &a, &b);
    int ans = 0;
    // 11
    for (int i = 1; i <= min(a, b); i *= 2) {
        int msk = i - 1;
        int upper = i - 1 + i;
        int take = min(upper, a);
        ans = max(ans, take & msk);
        take = min(upper, b);
        ans = max(ans, take & msk);
    }
    // 10
    for (int i = 1; i <= a; i *= 2) {
        int take = min(b, i - 1);
        ans = max(ans, take);
    }
    for (int i = 1; i <= b; i *= 2) {
        int take = min(a, i - 1);
        ans = max(ans, take);
    }
    printf("%d\n", ans);
    return 0;
}