// #pragma GCC optimize ("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC target ("avx,avx2,fma")
#include <bits/stdc++.h>

using std::cin, std::cout, std::cerr;
using ll = long long;

struct Point {
    ll x, y;
    Point operator -(Point p) {
        return {x - p.x, y - p.y};
    }
    ll Dot(Point p) {
        return x * p.x + y * p.y;
    }
    ll Length2() { return Dot(*this); }
};

int main() {
    std::ios::sync_with_stdio(false);
    int n; cin >> n;
    std::vector<Point> p(n);
    for(int i = 0; i < n; i ++)
        cin >> p[i].x >> p[i].y;
    std::vector<bool> del(n);

    auto simulate = [&]() {
        auto burst = del;
        std::vector<std::tuple<ll, int, int>> t;
        for(int i = 0; i < n; i ++)
            for(int j = i + 1; j < n; j ++)
                t.push_back({(p[i] - p[j]).Length2(), i, j});
        std::ranges::sort(t);
        for(auto [l, i, j] : t) {
            if(burst[i] || burst[j]) continue;
            burst[i] = burst[j] = true;
            if(i == 0) return j;
        }
        return -1;
    };

    int ans = 0;
    while(true) {
        int x = simulate();
        if(x == -1) break;
        del[x] = true;
        ans ++;
    }
    cout << ans << '\n';
}