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 javafx.util.Pair;

import java.io.*;
import java.math.*;
import java.util.*;
@SuppressWarnings("Duplicates")
// author @mdazmat9
public class Main{
    static Scanner sc = new Scanner(System.in);
    static PrintWriter out = new PrintWriter(System.out);
    public static void main(String[] args) throws IOException {
        int test = 1;
       // test=sc.nextInt();
        for (int ind = 0; ind < test; ind++) {
            solve();
        }
        out.flush();
    }
    static void solve() {
        int n=sc.nextInt();
       HashSet<Pair<Integer,Integer>> set=new HashSet<>();
       int[]x=new int[n];
       int[]y=new int[n];
       for(int i=0;i<n;i++){
           x[i]=sc.nextInt();
           y[i]=sc.nextInt();
           set.add(new Pair<>(x[i],y[i]));
       }
       int count=0;
       for(int i=0;i<n;i++){
           int x1=x[i],y1=y[i];
           for(int j=i+1;j<n;j++){
               int x2=x[j],y2=y[j];
               if((x1+x2)%2==1 || (y1+y2)%2==1 || (x1+x2)%2==-1 || (y1+y2)%2==-1){
                   continue;
               }
               Pair<Integer,Integer> p=new Pair<>((x1+x2)/2,(y1+y2)/2);
               if(set.contains(p)){
                //   out.println(p.getKey()+" "+p.getValue());
                   count++;
               }
           }
       }
       out.println(count);

    }


    static int[] intarray(int n){ int [] a=new int[n];for(int i=0;i<n;i++)a[i]=sc.nextInt();return a; }
    static void sort(int[]a){ shuffle(a);Arrays.sort(a);}
    static void sort(long[]a){ shuffle(a);Arrays.sort(a);}
    static long[] longarray(int n){ long [] a=new long[n];for(int i=0;i<n;i++)a[i]=sc.nextLong();return a; }
    static ArrayList<Integer> intlist(int n){ArrayList<Integer> list=new ArrayList<>();for(int i=0;i<n;i++)list.add(sc.nextInt());return list; }
    static ArrayList<Long> longlist(int n){ArrayList<Long> list=new ArrayList<>();for(int i=0;i<n;i++)list.add(sc.nextLong());return list; }
    static int[][] int2darray(int n,int m){ int [][] a=new int[n][m];for(int i=0;i<n;i++){ for(int j=0;j<m;j++){ a[i][j]=sc.nextInt(); } }return a; }
    static long[][] long2darray(int n,int m){ long [][] a=new long[n][m];for(int i=0;i<n;i++){ for(int j=0;j<m;j++){ a[i][j]=sc.nextLong(); } }return a; }
    static char[][] char2darray(int n,int m){ char [][] a=new char[n][m];for(int i=0;i<n;i++){ String s=sc.next(); a[i]=s.toCharArray(); }return a; }

    static double pi=3.14159265358979323846264;
    public static double logb( double a, double b ) {return Math.log(a) / Math.log(b); }
    static long fast_pow(long a, long b,long abs) {
        if(b == 0) return 1L;
        long val = fast_pow(a, b / 2,abs);
        if(b % 2 == 0) return val * val % abs;
        else return val * val % abs * a % abs;
    }
    static long abs = (long)1e9 + 7;
    static   void shuffle(int[] a) { int n = a.length;for(int i = 0; i < n; i++) { int r = i + (int) (Math.random() * (n - i));int tmp = a[i];a[i] = a[r];a[r] = tmp; } }
    static   void shuffle(long[] a) { int n = a.length;for(int i = 0; i < n; i++) { int r = i + (int) (Math.random() * (n - i));long tmp = a[i];a[i] = a[r];a[r] = tmp; } }
    static long gcd(long a , long b) {
        if(b == 0) return a;
        return gcd(b , a % b);
    }
}

class Scanner {
    public BufferedReader reader;
    public StringTokenizer st;
    public Scanner(InputStream stream) {
        reader = new BufferedReader(new InputStreamReader(stream));
        st = null;
    }
    public String next() {
        while (st == null || !st.hasMoreTokens()) {
            try {
                String line = reader.readLine();
                if (line == null) return null;
                st = new StringTokenizer(line);
            } catch (Exception e) {
                throw (new RuntimeException());
            }
        }
        return st.nextToken();
    }
    public int nextInt() {
        return Integer.parseInt(next());
    }
    public long nextLong() {
        return Long.parseLong(next());
    }
    public double nextDouble() {
        return Double.parseDouble(next());
    }
}
