/*
	B - The Sparsest Number in Between
*/

#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp> 

using namespace std;
using namespace __gnu_pbds;

typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update > pbds;
// find_by_order, order_by_key

#define sp << " " << 
#define ll unsigned long long
#define ld long double
#define pb push_back
#define F first
#define S second
#define PI 3.1415926535897932384626

#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sortall(x) sort(all(x))
#define sortrall(x) sort(rall(x))

#define printv(v) for(auto x : v) cout << x << " "; cout << "\n"
#define printm(m) for(auto x : m) cout << x.F sp x.S << "\n"

#define make_unique(x) sortall(x); (x).resize(unique(all(x)) - (x).begin())
#define numtobin(n) bitset<64>(n).to_string() 
#define bintoint(bin_str) stoi(bin_str, nullptr, 2)
#define bintoll(bin_str) stoll(bin_str, nullptr, 2)

struct custom_hash {
    static uint64_t splitmix64(uint64_t x) {
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};

template<typename T1, typename T2>
using safe_map = unordered_map<T1, T2, custom_hash>;

template<typename T>
using safe_set = unordered_set<T, custom_hash>;

template<typename T>
void debug(T x) { cerr << x << endl; }

template<typename T, typename... Args>
void debug(T x, Args... args) { cerr << x << " "; debug(args...); }

void fastIO() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);
}

void fraction() {
    cout.unsetf(ios::floatfield); 
    cout.precision(10); 
    cout.setf(ios::fixed,ios::floatfield);
}

void yn(bool res, bool cap = true) {
    vector<string> s = {"Yes", "YES", "No", "NO"};
    cout << ((res) ? s[0 + cap] : s[2 + cap]) << "\n";
}

void chmin(ll &x, ll y) { x = min(x, y); }
void chmax(ll &x, ll y) { x = max(x, y); }

inline ll nxt() { ll x; cin >> x; return x;}
inline ld nxtD() { ld x; cin >> x; return x;}
inline string nxtStr() { string x; cin >> x; return x;}

const int mod = 1e9 + 7;
const int INF = 1e9;
const ll LINF = 1e18;

void proc(){

}
// stress testing 
int sol(int x, int y) {
    int ans = x;
    int cnt = __builtin_popcount(x);
    while(y >= x) {
        int r = __builtin_popcount(x);
        if(cnt > r) {
            cnt = r;
            ans = x;
        }
        x++;
    }

    return ans;
}

void solve(int xl = 1, int xr = 1) {
    ll a, b; cin >> a >> b;
    // ll a = xl, b = xr;
    ll ans = a;
    bool p = false;

    auto countBit = [&](ll x) ->int {
        int res = 0;
        while(x){
            if(x & 1) res++;
            x >>= 1;
        }
        return res;
    };

    for(int i = 0; i < 64; i++) {
        ll p = (1ll << i);
        if(a <= p && p <= b) {
            cout << p << "\n";
            return;
        }
    }

    int l = countBit(a);

    for(int i = 64; i >= 0; i--) {
        if ((a >> i) & 1) p = true;
        if(!((a >> i) & 1) && ((b >> i) & 1) && p) {
            ll tmp = a;
            int l = i;
            while(i--) {
                if((tmp >> i) & 1)
                    tmp ^= (1ll << i);
            }

            for(int j = 0; j <= l; j++) {
                if((tmp | (1ll << j)) >= a) {
                    tmp |= (1ll << j);
                    a = tmp;
                    break;
                }
            }
            break;
        }
    }    
    int r = countBit(a);

    if(r == l) ans = min(a, ans);
    else if(l > r) ans = a;

    cout << ans << "\n";
    // ll chk = sol(xl, xr);
    // yn(chk == ans);
    // debug(xl, xr, ans, sol(xl, xr));
}

int main() {
    fastIO(); 
    proc();

    int tc = 1;
    // tc = nxt();
    for (int t = 1; t <= tc; t++) {
        // cout << "Case " << t << ": ";
        solve();
    }

    // for(int i = 1; i <= 50; i++) {
    //     for(int j = i; j <= 50; j++) {
    //         solve(i, j);
    //     }
    // }
}