#include <bits/stdc++.h>
#define NIL (-1)
#define ll long long
using namespace std;
const int64_t MOD = 1e9 + 7;
const int INF = INT_MAX;
const double PI = acos(-1.0);

int main() {
	ll N;
	cin >> N;
	
	bitset<64> bs(N);
	bool b = 0;
	for (int i = bs.size()-1; i >= 0; i--) {
		if (bs[i]) {
			if (!b) b = 1;
			else bs[i] = 0;
		}
	}

	ll ans = bs.to_ullong();
	cout << ans << endl;
}