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.
//package main;

import java.io.*;
import java.util.*;
import java.math.*;

public final class Main {
    BufferedReader br;
    StringTokenizer stk;
    
    public static void main(String[] args) throws Exception {
        new Main().run();
    }
    
    {
        stk = null;
        br = new BufferedReader(new InputStreamReader(System.in));
    }
    
    long mod = 998244353;
    StringBuilder res = new StringBuilder(1000005);
    void run() throws Exception {
        int n = ni();
        long[] pow = new long[45];
        pow[0] = 1;
        for(int i = 1; i < 45; i++) {
            pow[i] = pow[i - 1] << 1;
        }
        
        long[] a = new long[n];
        HashMap<Long, Integer> map = new HashMap<>();
        for(int i = 0; i < n; i++) {
            long num = nl();
            a[i] = num;
            map.put(num, map.getOrDefault(num, 0) + 1);
        }
        
        long count = 0;
        for(int i = 0; i < n; i++) {
            for(int j = 0; j < pow.length; j++) {
                if(pow[j] <= a[i]) {
                    continue;
                }
                long req = pow[j] - a[i];
                long COUNT = map.getOrDefault(req, 0);
                if(req == a[i]) {
                    COUNT--;
                }
                count += COUNT;
            }
        }
        
        System.out.println(count / 2);
    }
    
    //Reader & Writer
    String nt() throws Exception {
        if (stk == null || !stk.hasMoreTokens())
            stk = new StringTokenizer(br.readLine(), " ");
        return stk.nextToken();
    }

    char[] nc() throws Exception {
        return nt().toCharArray();
    }

    int ni() throws Exception {
        return Integer.parseInt(nt());
    }

    long nl() throws Exception {
        return Long.parseLong(nt());
    }
    
    double nd() throws Exception {
        return Double.parseDouble(nt());
    }
    
    //Some Misc methods
    long get(int l, int r, long[] a) {
        return l == 0 ? a[r] : a[r] - a[l - 1];
    }
    
    void shuffle(long[] a) {
        Random r = new Random();
        for(int i = 0; i < a.length; i++) {
            int idx = r.nextInt(a.length);
            long temp = a[i];
            a[i] = a[idx];
            a[idx] = temp;
        }
    }
    
    void reverse(long[] a) {
        for(int i = 0, j = a.length - 1; i < j; i++, j--) {
            long temp = a[i];
            a[i] = a[j];
            a[j] = temp;
        }
    }
    
    void print(int[] a) {
        System.out.println(Arrays.toString(a));
    }
}