10
-2 1
2 -2
-1 -2
0 0
2 -1
0 -2
2 2
0 2
-1 -1
1 -2
 40
-8 24
2 -1
1 -18
72 -70
5 -4
-308 436
-19 40
36 -35
-178 265
-1 2
-7 30
-1 0
3 -2
200 -285
17 -16
-35 74
0 -4
-86 106
-1 4
-7 6
0 1
-5 4
-2 3
6 -5
-4 5
181 -262
76 -118
0 0
-7 18
-58 104
-5 6
-6 12
-3 4
1 0
11 -10
-86 130
-3 6
153 -236
-183 270
-33 64
 5
0 -1
0 -2
0 -3
0 -4
0 -5
 10
0 1
-1 -1
1 1
-1 0
1 -1
-2 -1
-2 2
-2 0
0 -2
0 -1
 20
-1 18
-2 5
-5 4
2 -33
9 -18
0 0
11 -22
2 0
-1 2
-4 41
1 6
1 -2
6 -12
0 1
-3 6
3 -6
3 -8
-1 4
2 -5
1 0
 10
2 1
-1 0
-2 -1
-1 1
0 2
2 -2
0 0
-2 -2
0 -2
-2 1
 20
-3 -3
0 4
-3 1
1 1
-1 2
-4 4
3 -1
-3 0
0 2
4 0
2 3
2 4
4 -3
-4 3
-1 1
1 3
-2 4
1 -2
1 -1
3 0
 3
0 0
0 -1
0 1
 10
2 1
-1 1
0 0
-3 1
-2 -3
-1 -2
-1 -1
1 2
3 -2
0 -2
 3
3 3
1 2
1 1
 4
0 0
1 0
2 0
3 0
 9
1 1
1 0
0 1
0 0
-1 0
-1 1
-1 -1
1 -1
0 -1
 7
1 1
-1 -1
1 0
0 1
-1 0
0 -1
0 0

4
 57
 4
 5
 21
 4
 10
 1
 1
 0
 2
 8
 3

import java.util.Scanner;
import java.util.List;
import java.io.IOException;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.Comparator;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Collections;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 * @author @zhendeaini6001
 */
public class Main {
	public static void main(String[] args) {
		InputStream inputStream = System.in;
		OutputStream outputStream = System.out;
		Scanner in = new Scanner(inputStream);
		PrintWriter out = new PrintWriter(outputStream);
		TaskB solver = new TaskB();
		solver.solve(1, in, out);
		out.close();
	}
}

class TaskB {

    public void solve(int testNumber, Scanner in, PrintWriter out) {
        long res = 0;
        int n = in.nextInt();
        boolean [][] record = new boolean[2002][2002];
        ArrayUtils.fill(record, false);
        List<Pair<Integer, Integer> > list = new ArrayList<Pair<Integer, Integer>>();
        for (int i = 0; i < n; ++i){
            int a = in.nextInt();
            int b = in.nextInt();
            a += 1000; b += 1000;
            record[a][b] = true;
            list.add(Pair.makePair(a, b));
        }
        Collections.sort(list);
        for (int i = 0; i < list.size(); ++i){
            for (int j = i + 1; j < list.size(); ++j){
                if (i == j){
                    continue;
                }else{
                    int newa = list.get(j).first * 2 - list.get(i).first;
                    int newb = list.get(j).second * 2 - list.get(i).second;
                    if (newa >= 0 && newa < 2002 && newb >= 0 && newb < 2002 && record[newa][newb]){
                        ++res;
                    }
                    newa = list.get(i).first * 2 - list.get(j).first;
                    newb = list.get(i).second * 2 - list.get(j).second;
                    if (newa >= 0 && newa < 2002 && newb >= 0 && newb < 2002 && record[newa][newb]){
                        ++res;
                    }
                }
            }
        }
        out.println(res / 2);
        return;
    }
}

class ArrayUtils {

    public static void fill(boolean[][] array, boolean value) {
        for (boolean[] row : array)
            Arrays.fill(row, value);
    }

    }

class Pair<U, V> implements Comparable<Pair<U, V>> {
    public U first;
    public V second;

    public static <U, V> Pair<U, V> makePair(U first, V second) {
        return new Pair<U, V>(first, second);
    }

    private Pair(U first, V second) {
        this.first = first;
        this.second = second;
    }

    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Pair pair = (Pair) o;

        return !(first != null ? !first.equals(pair.first) : pair.first != null) && !(second != null ? !second.equals(pair.second) : pair.second != null);

    }

    public int hashCode() {
        int result = first != null ? first.hashCode() : 0;
        result = 31 * result + (second != null ? second.hashCode() : 0);
        return result;
    }

    public String toString() {
        return "(" + first + "," + second + ")";
    }

    public int compareTo(Pair<U, V> o) {
        int value = ((Comparable<U>) first).compareTo(o.first);
        if (value != 0)
            return value;
        return ((Comparable<V>) second).compareTo(o.second);
    }
}

