#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	vector<int>x(n), y(n);
	rep(i, n)cin >> x[i] >> y[i];
	map<pair<P, P>, int>mp;
	long long ans = 0;
	rep(i, n)rep2(j, i + 1, n) {
		int dx = x[j] - x[i];
		int dy = y[j] - y[i];

		if (0 == dx) {
			dy = 1;
		}
		else if (0 == dy) {
			dx = 1;
		}
		else {
			if (dx < 0) {
				dx *= -1;
				dy *= -1;
			}
			int g = gcd(dx, dy);
			dx /= g;
			dy /= g;
		}
		if (dy > 0) {
			P k0 = { dy,-dx };
			P k1 = { x[i] + x[j],y[i] + y[j] };
			ans += mp[{k0, k1}];
		}
		else {
			P k0 = { -dy,dx };
			P k1 = { x[i] + x[j],y[i] + y[j] };
			ans += mp[{k0, k1}];
		}
		//cout << dx << "_" << dy << endl;
		P k0 = { dx,dy };
		P k1 = { x[i] + x[j],y[i] + y[j] };
		mp[{k0, k1}]++;
	}
	cout << ans << endl;
	return 0;
}