#include <bits/stdc++.h>

//#include <atcoder/all>
#define For(i, a, b) for (int(i) = (int)(a); (i) < (int)(b); ++(i))
#define rFor(i, a, b) for (int(i) = (int)(a)-1; (i) >= (int)(b); --(i))
#define rep(i, n) For((i), 0, (n))
#define rrep(i, n) rFor((i), (n), 0)
#define fi first
#define se second
using namespace std;
typedef long long lint;
typedef unsigned long long ulint;
typedef pair<int, int> pii;
typedef pair<lint, lint> pll;
template <class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}
template <class T>
bool chmin(T &a, const T &b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template <class T>
T div_floor(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a >= 0 ? a / b : (a + 1) / b - 1;
}
template <class T>
T div_ceil(T a, T b) {
    if (b < 0) a *= -1, b *= -1;
    return a > 0 ? (a - 1) / b + 1 : a / b;
}

constexpr lint mod = 1000000007;
constexpr lint INF = mod * mod;
constexpr int MAX = 200010;

int main() {
    int n;
    scanf("%d", &n);
    lint x[n], y[n];
    rep(i, n) scanf("%lld%lld", &x[i], &y[i]);
    vector<pair<lint, pii>> ps;
    rep(i, n) For(j, i + 1, n) {
        lint d = (x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]);
        ps.push_back({d, {i, j}});
    }
    sort(ps.begin(), ps.end());
    bool used[n];
    memset(used, false, sizeof(used));
    int ans = 0;
    for (auto p : ps) {
        auto [i, j] = p.se;
        if (i == 0 && !used[j]) {
            ++ans;
            used[j] = true;
        } else if (!used[i] && !used[j]) {
            used[i] = used[j] = true;
        }
    }
    printf("%d\n", ans);
}