#include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using vi = vector<i64>;
using vvi = vector<vi>;

using ii = pair<int, int>;
const int nax = 1001;
vector<ii> b[nax][nax];

bool valid(int i, int j) {
    return 0 <= i && i < nax && 0 <= j && j < nax;
}

int dist2(int x, int y, int xx, int yy) {
    return (x - xx) * (x - xx) + (y - yy) * (y - yy);
}

int main() {
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
        int x, y;
        cin >> x >> y;
        int xx = x / 20;
        int yy = y / 20;
        int ok = 1;
        for (int dx = -1; dx <= 1; dx++) {
            for (int dy = -1; dy <= 1; dy++) {
                if (valid(xx + dx, yy + dy)) {
                    for (ii k: b[xx + dx][yy + dy]) {
                        if (dist2(k.first, k.second, x, y) < 400) {
                            ok = 0;
                        }
                    }
                }
            }
        }
        if (ok) {
            b[xx][yy].push_back(ii(x, y));
        }
    }

    int cnt = 0;
    for (int i = 0; i < nax; i++) {
        for (int j = 0; j < nax; j++) {
            cnt += b[i][j].size();
        }
    }
    cout << cnt << endl;
}