#include <bits/stdc++.h>
using namespace std;
template <typename T> using vec = vector<T>;
template <typename T> using vvec = vector<vector<T>>;

int main() {
    int n; cin >> n;
    vec<array<int, 2>> bal(n);
    for (auto &[x, y]: bal) cin >> x >> y;

    using dist_t = array<int, 3>;
    priority_queue<dist_t, vector<dist_t>, greater<dist_t>> que;
    for (int i = 0; i < n; ++i) {
        for (int j = i + 1; j < n; ++j) {
            int ax = bal[i][0], ay = bal[i][1];
            int bx = bal[j][0], by = bal[j][1];
            int dx = abs(ax - bx), dy = abs(ay - by);

            int dist = 0;
            if (ax == bx || ay == by) {
                dist = (max(dx, dy) + 1) / 2;
            }
            else {
                dist = (max(dx, dy)) / 2 + 1;
            }

            que.push({ dist, i, j });
        }
    }

    int ans = 0;

    vec<bool> used(n, false);
    while (que.size()) {
        auto [d, a, b] = que.top(); que.pop();
        if (used[a] || used[b]) continue;

        tie(a, b) = make_tuple(min(a, b), max(a, b));
        used[a] = a != 0;
        used[b] = true;

        ans += a == 0;
    }

    cout << ans << endl;
}