#include <iostream>
#include <algorithm>
#include <vector>

using lint = long long;

void solve() {
    int n;
    std::cin >> n;

    std::vector<std::pair<lint, lint>> ps(n);
    for (auto& [x, y] : ps) std::cin >> x >> y;

    std::vector<std::tuple<lint, int, int>> events;
    for (int i = 0; i < n; ++i) {
        auto [xi, yi] = ps[i];
        for (int j = 0; j < i; ++j) {
            auto [xj, yj] = ps[j];

            auto dx = xi - xj,
                 dy = yi - yj;

            events.emplace_back(dx * dx + dy * dy, j, i);
        }
    }

    std::sort(events.begin(), events.end());

    std::vector<bool> erased(n, false);
    int ans = 0;
    for (auto [t, i, j] : events) {
        if (erased[i] || erased[j]) continue;

        if (i == 0) {
            ++ans;
            erased[j] = true;
        } else {
            erased[i] = erased[j] = true;
        }
    }

    std::cout << ans << "\n";
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}