typedef long long ll;
typedef long double ld;
#include <bits/stdc++.h>
using namespace std;
#define int long long

signed main(){
    ll a,b;
    std::cin >> a>>b;
    if(__builtin_clzll(a)==__builtin_clzll(b)){
        std::cout << (1<<(63-__builtin_clzll(a)))-1 << std::endl;
    }else{
        std::cout <<         min(a,b) << std::endl;
    }
}