#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
#define rep(i, a, b) for(ll i = a; i < b; ++i)
#define rrep(i, a, b) for(ll i = a; i >= b; --i)
constexpr ll inf = 4e18;
struct SetupIO {
    SetupIO() {
        ios::sync_with_stdio(0);
        cin.tie(0);
        cout << fixed << setprecision(30);
    }
} setup_io;
int main(void) {
    int n;
    cin >> n;
    vector<ll> x(n), y(n);
    rep(i, 0, n) {
        cin >> x[i] >> y[i];
    }
    vector<pair<ll, P>> v;
    rep(i, 0, n) {
        rep(j, i + 1, n) {
            v.push_back({(x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]), {i, j}});
        }
    }
    sort(v.begin(), v.end());
    vector<bool> flag(n);
    ll ans = 0;
    for(const auto& p : v) {
        if(flag[p.second.first] or flag[p.second.second]) continue;
        if(p.second.first == 0) {
            ans++;
        } else {
            flag[p.second.first] = true;
        }
        flag[p.second.second] = true;
    }
    cout << ans << '\n';
}