#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
using pint = pair<int, int>;
using plint = pair<lint, lint>;
struct fast_ios { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
template<typename T> istream& operator>>(istream &is, vector<T> &vec){ for (auto &v : vec) is >> v; return is; }
template<typename T> ostream& operator<<(ostream &os, const vector<T> &vec){ os << "["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream& operator<<(ostream &os, const set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream& operator<<(ostream &os, const unordered_set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream& operator<<(ostream &os, const multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream& operator<<(ostream &os, const unordered_multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T1, typename T2> ostream& operator<<(ostream &os, const pair<T1, T2> &pa){ os << "(" << pa.first << "," << pa.second << ")"; return os; }
template<typename TK, typename TV> ostream& operator<<(ostream &os, const map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename TK, typename TV> ostream& operator<<(ostream &os, const unordered_map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename T> void ndarray(vector<T> &vec, int len) { vec.resize(len); }
template<typename T, typename... Args> void ndarray(vector<T> &vec, int len, Args... args) { vec.resize(len); for (auto &v : vec) ndarray(v, args...); }
template<typename T> void Max(T &m, const T q) { if (m < q) m = q; }
template<typename T> void Min(T &m, const T q) { if (m > q) m = q; }
template<typename T1, typename T2> pair<T1, T2> operator+(pair<T1, T2> &l, pair<T1, T2> &r) { return make_pair(l.first + r.first, l.second + r.second); }
template<typename T1, typename T2> pair<T1, T2> operator-(pair<T1, T2> &l, pair<T1, T2> &r) { return make_pair(l.first - r.first, l.second - r.second); }
#define dbg(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ") " << __FILE__ << endl;

int N;
vector<lint> A;

lint inverse(lint q)
{
    lint ans = 0;
    bool flg = false;
    IREP(d, 60)
    {
        if ((q >> d) & 1LL) flg = true;
        if (!((q >> d) & 1LL) && flg) ans += 1LL << d;
    }
    return ans + 1;
}

int main()
{
    cin >> N;
    A.resize(N);
    cin >> A;
    sort(A.begin(), A.end());
    vector<int> used(N);
    multiset<int> cand;
    for (auto v : A) cand.insert(v);
    cand.insert(2E9);
    int ans = 0;
    IREP(i, N)
    {
        lint inv = inverse(A[i]);
        auto ptr1 = cand.lower_bound(A[i]);
        if (*ptr1 == A[i])
        {
            cand.erase(ptr1);
            auto ptr2 = cand.lower_bound(inv);
            if (*ptr2 == inv)
            {
                cand.erase(ptr2);
                ans++;
            }
            else
            {
                cand.insert(A[i]);
            }
        }
    }
    // IREP(i, N) if (!used[i])
    // {
    //     lint inv = inverse(A[i]);
    //     int pos = distance(A.begin(), prev(upper_bound(A.begin(), A.end(), inv)));
    //     if (pos < 0 || pos >= i) continue;
    //     while (pos >= 0 && used[pos]) pos--;
    //     if (pos < 0) continue;
    //     if (A[pos] == inv)
    //     {
    //         used[pos] = 1;
    //         ans++;
    //     }
    // }
    cout << ans << endl;
}


Measured memory_bytes: 12032