#include //#include using namespace std; //using namespace atcoder; //using mint = modint1000000007; //const int mod = 1000000007; //using mint = modint998244353; //const int mod = 998244353; //const int INF = 1e9; //const long long LINF = 1e18; #define rep(i, n) for (int i = 0; i < (n); ++i) #define rep2(i,l,r)for(int i=(l);i<(r);++i) #define rrep(i, n) for (int i = (n-1); i >= 0; --i) #define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i) #define all(x) (x).begin(),(x).end() #define allR(x) (x).rbegin(),(x).rend() #define endl "\n" #define P pair template inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; } template inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; } int calc(int x) { int ret = 0; while (x) { x /= 2; ret++; } return ret; } int main() { ios::sync_with_stdio(false); cin.tie(nullptr); int a, b; cin >> a >> b; if (a > b)swap(a, b); int pa = calc(a); int pb = calc(b); if (pa == pb) { int ans = 1; rep(i, pa - 1)ans *= 2; cout << ans - 1 << endl; } else { cout << a << endl; } return 0; }