#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)

using std::cin;
using std::cout;
using std::vector;
using P = std::pair<int, int>;

int main() {
    int a, b;
    cin >> a >> b;
    
    if (a == b) {
        cout << std::min(std::min(a, a-1), a^(a-1)) << '\n';
        return 0;
    }
    
    if (a > b) std::swap(a, b);
    
    cout << std::min(std::min(a, a+1), a^(a+1)) << '\n';
    
    return 0;
}