#include <bits/stdc++.h>

#define rep(i, n) for (int (i) = 0; (i) < (int)(n); (i)++)

const int dx[] = {1, 0, -1, 0};
const int dy[] = {0, 1, 0, -1};
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef pair<int, int> pii;

const int MAXN = 122222;
ll X[MAXN], Y[MAXN];

vector<pii> pos[2222][2222];

ll square(int x) {return x*x;}

bool in(const pii& p, const pii& q) {
    return square(p.first-q.first) + square(p.second-q.second) < 20*20;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N;
    cin >> N;
    for (int i = 0; i < N; i++) {
        cin >> X[i] >> Y[i];
    }
    int ans = 0;
    for (int i = 0; i < N; i++) {
        int y = Y[i]/10;
        int x = X[i]/10;
        bool ng = false;
        for (int dx = -3; dx <= 3; dx++) {
            for (int dy = -3; dy <= 3; dy++) {
                int nx = x+dx;
                int ny = y+dy;
                if (nx < 0 || ny < 0) continue;
                for (auto p : pos[ny][nx]) {
                    if (in(p, pii(Y[i], X[i]))) {
                        ng = true;
                        break;
                    }
                }
                if (ng) break;
            }
            if (ng) break;
        }
        if (!ng) {
            ans++;
            pos[y][x].push_back(pii(Y[i], X[i]));
        }
    }
    cout << ans << endl;
    return 0;
}