#include <bits/stdc++.h>
using namespace std;
string itosm(long long x) {
  if (x == 0) return "0";
  string res = "";
  while (x > 0) {
    res += ((x % 10) + '0');
    x /= 10;
  }
  reverse(res.begin(), res.end());
  return res;
}
long long stoim(string str) {
  long long res = 0;
  int p = 0;
  if (str[0] == '-') p++;
  for (int i = p; i < str.length(); i++) {
    res *= 10;
    res += (str[i] - '0');
  }
  return res;
}
const long long infll = 1e18 + 3;
const int inf = 1009000999;
const long double eps = 1e-7;
const int maxn = 1e6 + 1146;
const int baseint = 1000200013;
const long long basell = 1e18 + 3;
const long double PI = acos(-1.0);
const long long mod = 998244353;
long long binpow(long long x, long long st) {
  if (st == 0) return 1;
  if (st & 1) return binpow(x, st - 1) * x % mod;
  long long res = binpow(x, st >> 1);
  return res * res % mod;
}
int a[maxn];
void solve() {
  int n;
  cin >> n;
  map<int, int> m;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    m[a[i]]++;
  }
  int ans = 0;
  for (int i = 0; i < n; i++) {
    bool can = 0;
    for (int j = 0; j <= 30; j++) {
      int x = (1 << j);
      if (x <= a[i]) continue;
      if (m[x - a[i]] > 0) {
        if (m[x - a[i]] == 1 && x == a[i] << 1) continue;
        can = 1;
        break;
      }
    }
    if (!can) ans++;
  }
  cout << ans;
}
int main() {
  srand(time(0));
  ios_base::sync_with_stdio(0);
  ;
  cin.tie(0);
  cout.tie(0);
  solve();
  return 0;
}
