#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
//#pragma warning(disable : 4996)

//#define ATCODER
#ifdef ATCODER
#include<atcoder/all>
using namespace atcoder;
#endif


#include <algorithm>
#include <utility>
#include <vector>



#include <limits.h>
#include <math.h>
#include <time.h>

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#include <cassert>
#include <numeric>
#include <type_traits>

using namespace std;

#ifdef _MSC_VER
#include"stdafx.h"
#include <intrin.h>
#define __builtin_popcount __popcnt
#define __builtin_popcountll __popcnt64
void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
	cerr << " " << (H);
	debug_out(T...);
}
#define DEBUG(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define DEBUG(...) 42
#endif

#define ll long long
#define REP(i, n) for (ll i = 0; i < (n); ++i)
#define REPR(i, n) for (ll i = n - 1; i >= 0; --i)
#define FOR(i, m, n) for (ll i = m; i < n; ++i)
#define VSORT(v) sort(v.begin(), v.end());
#define VREVERSE(v) reverse(v.begin(), v.end())

#define print(x) cout << (x) << '\n'
#define spa <<" "<<
#define lb(v, n) lower_bound(v.begin(), v.end(), (n))
#define ub(v, n) upper_bound(v.begin(), v.end(), (n))
//#define int long long
#define double long double
#define all(x) (x).begin(), (x).end()
#define print_space(v) REP(i, v.size()) cout << v[i] << " \n"[i==(int)v.size()-1]
template <typename T1, typename T2> inline void chmin(T1 & a, T2 b) { if (a > b) a = b; }
template <typename T1, typename T2> inline void chmax(T1& a, T2 b) { if (a < b) a = b; }
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
std::random_device rd;
std::mt19937 mt(rd());
constexpr ll MOD = 1e9 + 9;
constexpr int MAX = 500050;
const double pi = acos(-1);
constexpr double EPS = 1e-8;
constexpr ll LINF = 1e17 + 1;
constexpr int INF = 1e9 + 1;

using point = complex<double>;
void solve() {
	int N; cin >> N;
	vector<point>ps;
	REP(i, N) {
		int x, y; cin >> x >> y;
		ps.push_back(point(x,y));
	}
	vector<pair<pii, double>>v;
	REP(i, N)FOR(j, i + 1, N) {
		double d = abs(ps[i] - ps[j]);
		v.push_back({ {i,j},d });
	}
	using piid = pair<pii, double>;
	sort(all(v), [](piid &a, piid &b) {
		return a.second < b.second;
	});
	set<int>st;
	int ans = 0;
	for (auto p : v) {
		int a = p.first.first, b = p.first.second;
		if (st.count(a) || st.count(b))continue;
		if (a > b)swap(a, b);
		if (a == 0) {
			st.insert(b);
			ans++;
		}
		else {
			st.insert(a);
			st.insert(b);
		}
	}
	print(ans);
}





signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);
	//int q; cin >> q; while (q--)
	solve();
}