#include <bits/stdc++.h>
using namespace std;
int pos[2017][2017];
vector<pair<int, int>> coin;
int N;
int main() {
	int ans = 0;
	for(int i = 0; i < 2017; i++) {
		for(int j = 0; j < 2017; j++) {
			pos[i][j] = -1;
		}
	}
	cin >> N;
	int X, Y, x, y, cx, cy;
	int c = -1;
	bool flag = true;
	for(int i = 0; i < N; i++) {
		cin >> X >> Y;
		for(int dy = -2; dy <= 2; dy++) {
			for(int dx = -2; dx <= 2; dx++) {
				x = (X / 10) + dx;
				y = (Y / 10) + dy;
				if(x < 0 || y < 0) continue;
				c = pos[x][y];
				if(c < 0) continue;
				cx = coin[c].first, cy = coin[c].second;
				if((cx - X) * (cx - X) + (cy - Y) * (cy - Y) < 400) {
					flag = false;
				}
			}
		}
		if(flag) {
			ans++;
			pos[X / 10][Y / 10] = coin.size();
			coin.push_back(pair<int, int>(X, Y));
		}
		flag = true;
	}
	cout << ans << endl;
	return 0;
}