#include <bits/stdc++.h>
using namespace std;
template <class T>
void rd(T& ret) {
  ret = 0;
  bool ok = 0, u = 0;
  for (;;) {
    int c = getchar();
    if (c >= '0' && c <= '9')
      ret = (ret << 3) + (ret << 1) + c - '0', ok = 1;
    else if (c == '-')
      u = 1;
    else if (ok) {
      if (u) ret *= -1;
      return;
    }
  }
}
long long pow_mod(long long p, long long n, long long mod) {
  long long ret = 1;
  for (; n; n >>= 1) {
    if (n & 1) ret = ret * p % mod;
    p = p * p % mod;
  }
  return ret;
}
template <class T>
bool chmin(T& a, const T& b) {
  return b < a ? a = b, 1 : 0;
}
template <class T>
bool chmax(T& a, const T& b) {
  return b > a ? a = b, 1 : 0;
}
int gcd(int a, int b) { return b ? gcd(b, a % b) : a; }
int main() {
  int n;
  cin >> n;
  long long k = 1, t, ans = -1;
  while (1) {
    t = (pow(2, k) - 1) * pow(2, k - 1);
    if (t > n) break;
    if (n % t == 0) ans = t;
    ++k;
  }
  cout << ans << endl;
  return 0;
}
