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

/**
 *      author:  Geloger
 *      created: 12.04.2019 22:45
**/

#include <bits/stdc++.h>

#ifdef LOCAL
#define _GLIBCXX_DEBUG
#endif // LOCAL

using ll = long long; using ld = long double; using ull = unsigned ll;

#define all(x) begin(x), end(x)
#define sz(x) (x).size()
#define pb(x) push_back(x)

constexpr int N = 15, inf = 1e9;

int a[3000 + 7][3000 + 7], x[3000 + 7], y[3000 + 7];

struct solution{
    int n;
    void solve(std::istream& in, std::ostream& out) {
        in >> n;
        for(int i = 0; i < n; ++i) {
            in >> x[i] >> y[i];
            a[x[i]][y[i]] = 1;
        }
        int ans = 0;
        for(int i = 0; i < n; ++i) {
            for(int j = i + 1; j < n; ++j) {
                int xx = x[i] + x[j], yy = y[i] + y[j];
                if(xx&1 || yy&1) continue;
                if(a[xx/2][yy/2]) ++ans;
            }
        }
        out << ans;
    }
};

int32_t main(){
    std::ios::sync_with_stdio(0),
    std::cin.tie(0), std::cout.tie(0),
    std::cout << std::setprecision(N) << std::fixed;

    #ifdef FILE_IO
    std::ifstream cin("input.txt");
    std::ofstream cout("output.txt");
    #endif // FILE_IO

    clock_t t = clock();

    #ifdef FILE_IO
    solution().solve(cin, cout);
    #else
    solution().solve(std::cin, std::cout);
    #endif // FILE_IO


    //std::cerr << std::endl << (clock()-t)*1.0/CLOCKS_PER_SEC;

    return 0;
}
