#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
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; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = false;
//---------------------------------//

int main() {
	int N;
	cin >> N;
	vector<int> X(N), Y(N);
	REP(i, N) scanf("%d %d", &X[i], &Y[i]);
	
	using tup = tuple<ll, int, int>;
	priority_queue<tup, vector<tup>, greater<tup>> pq;
	REP(i, N) FOR(j, i + 1, N) {
		const ll dx = X[j] - X[i], dy = Y[j] - Y[i];
		pq.emplace(dx * dx + dy * dy, i, j);
	}
	int ans = 0;
	vector<bool> alive(N, true);
	ll prevd = -1;
	vector<int> v;
	while (!pq.empty()) {
		auto [dist, x, y] = pq.top(); pq.pop();
		if (prevd != dist) {
			for (int i : v) alive[i] = false;
			prevd = dist;
		}
		if (!alive[x] || !alive[y]) continue;
		if (x == 0) {
			++ans;
			alive[y] = false;
		}
		else {
			v.emplace_back(x);
			v.emplace_back(y);
		}
	}
	cout << ans << endl;
}