You are given n points on a plane. All the points are distinct and no three of them lie on the same line. Find the number of parallelograms with the vertices at the given points.

Input

The first line of the input contains integer n (1 ≤ n ≤ 2000) — the number of points.

Each of the next n lines contains two integers (xi, yi) (0 ≤ xi, yi ≤ 109) — the coordinates of the i-th point.

Output

Print the only integer c — the number of parallelograms with the vertices at the given points.

Example

Input

4
0 1
1 0
1 1
2 0


Output

1

import java.io.*;
import java.math.BigInteger;
import java.util.*;
import java.util.Random;
import java.util.StringTokenizer;

public class Main {

    String fileName = "";
    //////////////////////    SOLUTION   SOLUTION  SOLUTION    //////////////////////////////
    Long INF = Long.MAX_VALUE;
    long MODULO = 1000_000_000 + 7;
    int MAX_VALUE = 1000_1000;
    int[][] steps = {{0, 1}, {1, 0}, {-1, 0}, {0, -1}};
    private final static Random rnd = new Random();
    double eps = 1e-4;

    void solve() throws IOException {
        long ans = 0;
        int n = readInt();
        long[] x = new long[n];
        long[] y = new long[n];
        for (int i=0; i<n; ++i){
            x[i] = readInt();
            y[i] = readInt();
        }
        Map<Long, Integer> mp = new HashMap<>();
        for (int i=0; i<n; ++i){
            for (int j=0; j<n; ++j){
                if (j == i) continue;
                long vectorX = x[j] - x[i];
                long vectorY = y[j] - y[i];
                long hash = (vectorX * 9822873 + vectorY * 1234829);
                mp.put(hash, mp.getOrDefault(hash, 0) + 1);
            }
        }
        for (Map.Entry<Long, Integer> entry: mp.entrySet()){
            long curVal = entry.getValue();
            ans += curVal*(curVal-1)/2;
        }
        out.println(ans / 4);
    }


    class Point{
        long x, y;

        public Point(long x, long y) {
            this.x = x;
            this.y = y;
        }
    }

    class Fenwik {
        int[] t;
        int n;
        Fenwik(int n){
            t = new int[n];
            this.n = n;
        }

        void inc(int r, int delta){
            for (; r < n; r = r | (r + 1)) t[r] += delta;
        }
        int getSum(int r){
            int res = 0;
            for (; r >=0; r = (r & (r + 1) ) - 1) res += t[r];
            return res;
        }
    }
    boolean isPrime(int n){
        for (int i=2; i*i<=n; ++i){
            if (n%i==0) return false;
        }
        return true;
    }
    class Edge implements Comparable<Edge>{
        int from, to, num, dist;
        Edge(int from, int to, int dist, int num){
            this.from = from;
            this.to = to;
            this.num = num;
            this.dist = dist;
        }

        @Override
        public int compareTo(Edge o) {
            return Integer.compare(this.dist, o.dist);
        }
    }


    class Segment{
        Point p1, p2;
        public Segment(Point p1, Point p2) {
            this.p1 = p1;
            this.p2 = p2;
        }
    }
    Point readPoint() throws IOException{
        return new Point(readInt(), readInt());
    }
    class Number implements Comparable<Number>{
        int x, cost;
        Number(int x, int cost){
            this.x = x;
            this.cost = cost;
        }

        @Override
        public int compareTo(Number o) {
            return Integer.compare(this.cost, o.cost);
        }
    }

    void readUndirectedGraph (int n, int m, int[][] graph) throws IOException{
        Edge[] edges = new Edge[m];
        int[] countEdges = new int[n];
        for (int i=0; i<m; ++i){
            int from = readInt() - 1;
            int to = readInt() - 1;
            countEdges[from]++;
            countEdges[to]++;
            edges[i] = new Edge(from, to, 0, 0);
        }
        for (int i=0; i<n; ++i) {
            graph[i] = new int[countEdges[i]];
        }
        for (int i=0; i<m; ++i){
            graph[edges[i].from][--countEdges[edges[i].from]] = edges[i].to;
            graph[edges[i].to][-- countEdges[edges[i].to]] = edges[i].from;
        }
    }
    class Vertex implements Comparable<Vertex>{
        int i, j, plus;
        Vertex(int i, int j, int plus){
            this.i = i;
            this.j = j;
            this.plus = plus;
        }

        @Override
        public int compareTo(Vertex o) {
            return Integer.compare(this.plus, o.plus);
        }
    }



    ///////////////////////////////////////////////////////////////////////////////////////////

    class Dsu{
        int[] parent;
        int countSets;
        Dsu(int n){
            parent = new int[n];
            countSets = n;
            for (int i=0; i<n; ++i){
                parent[i] = i;
            }
        }
        int findSet(int a){
            if (a == parent[a]) return a;
            parent[a] = findSet(parent[a]);
            return parent[a];
        }
        void unionSets(int a, int b){
            a = findSet(a);
            b = findSet(b);
            if (a != b){
                parent[a] = b;
                countSets--;
            }
        }
    }

    class SparseTable{
        int[][] rmq;
        int[] logTable;
        int n;
        SparseTable(int[] a){
            n = a.length;
            logTable = new int[n+1];
            for(int i = 2; i <= n; ++i){
                logTable[i] = logTable[i >> 1] + 1;
            }
            rmq = new int[logTable[n] + 1][n];
            for(int i=0; i<n; ++i){
                rmq[0][i] = a[i];
            }

            for(int k=1; (1 << k) < n; ++k){
                for(int i=0; i + (1 << k) <= n; ++i){
                    int max1 = rmq[k - 1][i];
                    int max2 = rmq[k-1][i + (1 << (k-1))];
                    rmq[k][i] = Math.max(max1, max2);
                }
            }
        }

        int max(int l, int r){
            int k = logTable[r - l];
            int max1 = rmq[k][l];
            int max2 = rmq[k][r - (1 << k) + 1];
            return Math.max(max1, max2);
        }
    }
    long checkBit(long mask, int bit){
        return (mask >> bit) & 1;
    }

    static int checkBit(int mask, int bit) {
        return (mask >> bit) & 1;
    }
    boolean isLower(char c){
        return c >= 'a' && c <= 'z';
    }

    ////////////////////////////////////////////////////////////



    int gcd(int a, int b){
        return b == 0 ? a : gcd(b, a%b);
    }
    long gcd(long a, long b){
        return b == 0 ? a : gcd(b, a%b);
    }
    double binPow(double a, int pow){
        if (pow == 0) return 1;
        if (pow % 2 == 1) {
            return a * binPow(a, pow - 1);
        } else {
            double c = binPow(a, pow / 2);
            return c * c;
        }
    }
    long binPow(long a, long b, long m) {
        if (b == 0) {
            return 1;
        }
        if (b % 2 == 1) {
            return ((a % m) * (binPow(a, b - 1, m) % m)) % m;
        } else {
            long c = binPow(a, b / 2, m);
            return (c * c) % m;
        }

    }
    int minInt(int... values) {
        int min = Integer.MAX_VALUE;
        for (int value : values) min = Math.min(min, value);
        return min;
    }

    int maxInt(int... values) {
        int max = Integer.MIN_VALUE;
        for (int value : values) max = Math.max(max, value);
        return max;
    }
    public static void main(String[] args) throws NumberFormatException, IOException {
        // TODO Auto-generated method stub
        new Main().run();
    }

    void run() throws NumberFormatException, IOException {
        solve();
        out.close();
    };

    BufferedReader in;
    PrintWriter out;

    StringTokenizer tok;
    String delim = " ";

    Main() throws FileNotFoundException {
        try {
            in = new BufferedReader(new FileReader("input.txt"));
            out = new PrintWriter("output.txt");
        } catch (Exception e) {
            if (fileName.isEmpty()) {
                in = new BufferedReader(new InputStreamReader(System.in));
                out = new PrintWriter(System.out);
            } else {
                in = new BufferedReader(new FileReader(fileName + ".in"));
                out = new PrintWriter(fileName + ".out");
            }

        }
        tok = new StringTokenizer("");
    }

    String readLine() throws IOException {
        return in.readLine();
    }

    String readString() throws IOException {
        while (!tok.hasMoreTokens()) {
            String nextLine = readLine();
            if (null == nextLine) {
                return null;
            }

            tok = new StringTokenizer(nextLine);
        }
        return tok.nextToken();
    }

    int readInt() throws NumberFormatException, IOException {
        return Integer.parseInt(readString());
    }
    byte readByte() throws NumberFormatException, IOException {
        return Byte.parseByte(readString());
    }
    int[] readIntArray (int n) throws NumberFormatException, IOException {
        int[] a = new int[n];
        for(int i=0; i<n; ++i){
            a[i] = readInt();
        }
        return a;
    }

    Integer[] readIntegerArray (int n) throws NumberFormatException, IOException {
        Integer[] a = new Integer[n];
        for(int i=0; i<n; ++i){
            a[i] = readInt();
        }
        return a;
    }

    long readLong() throws NumberFormatException, IOException {
        return Long.parseLong(readString());
    }

    double readDouble() throws NumberFormatException, IOException {
        return Double.parseDouble(readString());
    }
}