You are given n integers a1, a2, ..., an. Find the number of pairs of indexes i, j (i < j) that ai + aj is a power of 2 (i. e. some integer x exists so that ai + aj = 2x).

Input

The first line contains the single positive integer n (1 ≤ n ≤ 105) — the number of integers.

The second line contains n positive integers a1, a2, ..., an (1 ≤ ai ≤ 109).

Output

Print the number of pairs of indexes i, j (i < j) that ai + aj is a power of 2.

Examples

Input

4
7 3 2 1


Output

2


Input

3
1 1 1


Output

3

Note

In the first example the following pairs of indexes include in answer: (1, 4) and (2, 4).

In the second example all pairs of indexes (i, j) (where i < j) include in answer.
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.OutputStream;
import java.util.StringTokenizer;
import java.util.HashMap;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;
import java.io.BufferedOutputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author AEroui
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Kattio in = new Kattio(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskBB solver = new TaskBB();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskBB {
        public void solve(int testNumber, Kattio in, PrintWriter out) {
            int n = in.nextInt();
            int[] arr = new int[n];
            HashMap<Integer, Integer> cnt = new HashMap<>();
            long ans = 0;
            for (int i = 0; i < n; ++i) {
                arr[i] = in.nextInt();

                for (int j = 0; j < 32; ++j) {
                    int pow2 = 1 << j;
                    ans += cnt.getOrDefault(pow2 - arr[i], 0);
                }

                cnt.put(arr[i], cnt.getOrDefault(arr[i], 0) + 1);
            }

            out.println(ans);
        }

    }

    static class Kattio extends PrintWriter {
        private BufferedReader r;
        private String line;
        private StringTokenizer st;
        private String token;

        public Kattio(InputStream i) {
            super(new BufferedOutputStream(System.out));
            r = new BufferedReader(new InputStreamReader(i));
        }

        public Kattio(InputStream i, OutputStream o) {
            super(new BufferedOutputStream(o));
            r = new BufferedReader(new InputStreamReader(i));
        }

        public int nextInt() {
            return Integer.parseInt(nextToken());
        }

        private String peekToken() {
            if (token == null)
                try {
                    while (st == null || !st.hasMoreTokens()) {
                        line = r.readLine();
                        if (line == null) return null;
                        st = new StringTokenizer(line);
                    }
                    token = st.nextToken();
                } catch (IOException e) {
                }
            return token;
        }

        private String nextToken() {
            String ans = peekToken();
            token = null;
            return ans;
        }

    }
}

