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.util.*;
import java.lang.*;
import java.io.*;   
import java.math.*;
public class Prac{     
    static class InputReader { 
        private final InputStream stream;
        private final byte[] buf = new byte[8192];
        private int curChar, snumChars;
        public InputReader(InputStream st) {
            this.stream = st;
        } 
        public int read() {
            if (snumChars == -1)
                throw new InputMismatchException();
            if (curChar >= snumChars) {
                curChar = 0;
                try {
                    snumChars = stream.read(buf);
                } 
                catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (snumChars <= 0)
                    return -1;
            }
            return buf[curChar++];
        }
        public int ni() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        } 
        public long nl() {
            int c = read();
            while (isSpaceChar(c)) {
            c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            long res = 0;
            do {
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        } 
        public int[] nia(int n) {
            int a[] = new int[n];
            for (int i = 0; i < n; i++) {
                a[i] = ni();
            }
            return a;
        } 
        public String rs() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                    c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }
        public String nextLine() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            } while (!isEndOfLine(c));
            return res.toString();
        } 
        public boolean isSpaceChar(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        private boolean isEndOfLine(int c) {
            return c == '\n' || c == '\r' || c == -1;
        } 
    }
    public static class Key {

        private final int x;
        private final int y;

        public Key(int x, int y) {
            this.x = x;
            this.y = y;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (!(o instanceof Key)) return false;
            Key key = (Key) o;
            return x == key.x && y == key.y;
        }

        @Override
        public int hashCode() {
            int result = x;
            result = 31 * result + y;
            return result;
        }

    }
    static class Pair implements Comparable<Pair>{
            int x,y;
            Pair(int a,int b){
                    x=a;y=b;
            }
            @Override
            public int compareTo(Pair p) {
                    if(x==p.x) return y-p.y;
                    return x-p.x;
            }
    }

    static PrintWriter w = new PrintWriter(System.out);
    static long mod1=998244353L,mod=1000000007;
   
    public static void main(String [] args){
        InputReader sc=new InputReader(System.in); 
        int n=sc.ni();
        Pair arr[]=new Pair[n];
        for(int i=0;i<n;i++){
            arr[i]=new Pair(sc.ni(),sc.ni());
        }
        Pair ans[]=new Pair[n*n];
        int k=0;
        for(int i=0;i<n;i++){

            for(int j=i+1;j<n;j++){
                int dx=arr[i].x+arr[j].x;
                int dy=arr[i].y+arr[j].y;
                ans[k++]=new Pair(dx,dy);
                
            }
        }
        
        Arrays.sort(ans,0,k);
        long c=0,res=0;
        for(int i=0;i<k-1;i++){
            if(ans[i].x==ans[i+1].x&&ans[i].y==ans[i+1].y)c++;
            else{
                res+=((c)*(c-1))/2;
                c=1;
            }
        }
        res+=((c)*(c-1))/2;
        w.println(res);
        w.close();
    }
}
