#include <cassert>
#include <functional>
#include <set>
#include <ctime>
#include <cmath>
#include <climits>
#include <string>
#include <queue>
#include <map>
#include <vector>
#include <algorithm>
#include <iostream>
#include <cstdio>
#ifndef ONLINE_JUDGE //POJ
# include <random>
# include <array>
# define mkt make_tuple
# define empb emplace_back
#endif
#ifdef _LOCAL
# include "for_local.h"
#endif
using namespace std;
typedef unsigned int uint; typedef unsigned long long ull;
#define repi(_I, _B, _E) for(int _I = (_B); (_I) < (_E); ++ (_I))
#define rep(_I, _N) for(int _I = 0; (_I) < (_N); ++ (_I))
#define mkp make_pair
#define all(_X) (_X).begin(), (_X).end()
#define scani(_V) std::scanf("%d", &_V)
#define printi(_V) std::printf("%d", static_cast<int>(_V))

template<typename T>
T selfprod(T const& x, T const& y) { return x * x + y * y; }

signed main() {
	int n;
	cin >> n;

	int k = 0;
	vector<pair<int, int>> ps;
	vector<pair<int, int>> xs, ys;
	rep(i, n) {
		int x, y;
		cin >> x >> y;

		bool ok = true;
		vector<bool> vb(n, false);
		auto&& ranx = mkp(upper_bound(all(xs), mkp(x - 20, 0)), lower_bound(all(xs), mkp(x + 20, 0)));
		auto&& rany = mkp(upper_bound(all(ys), mkp(y - 20, 0)), lower_bound(all(ys), mkp(y + 20, 0)));
		for ( auto it = ranx.first; it != ranx.second; ++it ) {
			vb[it->second] = true;
		}
		for ( auto it = rany.first; it != rany.second; ++it ) {
			if ( vb[it->second] ) {
				auto const& p = ps[it->second];
				if ( selfprod(x - p.first, y - p.second) < ((10*2)*(10*2)) ) {
					ok = false; break;
				}
			}
		}
		if ( ok ) {
			ps.emplace_back(x, y);
			xs.emplace(lower_bound(all(xs), mkp(x, k)), mkp(x, k));
			ys.emplace(lower_bound(all(ys), mkp(y, k)), mkp(y, k));
			++k;
		}
	}
	cout << k  << endl;

	return 0;
}