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.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Collections;
import java.util.Hashtable;
import java.util.Vector;


public class Main {

    /**
     * @param args
     * @throws IOException 
     */
    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub
        BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
        //Scanner in=new Scanner(System.in);
        PrintWriter out=new PrintWriter(System.out);
        int n=Integer.parseInt(in.readLine());
        int[] x=new int[n];
        int[] y=new int[n];
        Hashtable<String,Integer> hash=new Hashtable<String, Integer>();
        for(int i=0; i<n; i++){
            String str=in.readLine();
            String[] cur=str.split(" ");
            x[i]=Integer.parseInt(cur[0]);
            y[i]=Integer.parseInt(cur[1]);
            Integer cnt=hash.get(str);
            if(cnt==null){
                hash.put(str,1);
            }
            else{
                hash.put(str,cnt+1);
            }
        }
        long count=0;
        for(int i=0; i<n; i++){
            for(int j=i+1; j<n; j++){
                int fX=(x[i]+x[j])/2;
                int fXmod=(x[i]+x[j])%2;
                int fY=(y[i]+y[j])/2;
                int fYmod=(y[i]+y[j])%2;
                if(fYmod==0 && fXmod==0){
                    String str=fX+" "+fY;
                    Integer cnt=hash.get(str);
                    if(cnt!=null){
                        count+=cnt;
                    }
                }
            }
        }
        out.println(count);
        out.close();
    }

}
