#include <bits/stdc++.h>
#define all(x) (x).begin(),(x).end()

using namespace std;
using ll = long long;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n;
    cin >> n;
    vector<int> x(n), y(n);
    for (int i = 0; i < n; i++) {
        cin >> x[i] >> y[i];
    }
    vector<pair<ll, pair<int,int>>> lines;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < i; j++) {
            lines.push_back({(x[i] - x[j]) * 1ll * (x[i] - x[j]) + (y[i] - y[j]) * 1ll * (y[i] - y[j]), {i, j}});
        }
    }
    sort(all(lines), greater<>());
    auto cw = [&] (int x1, int y1, int x2, int y2) {
        return 1ll * x1 * y2 == 1ll * x2 * y1;
    };
    double answer = 0;
    vector<vector<int>> used(n);
    for (auto& [len, p] : lines) {
        auto& [i, j] = p;
        bool good = true;
        for (int v : used[i]) {
            if (cw(x[i] - x[j], y[i] - y[j], x[i] - x[v], y[i] - y[v])) {
                good = false;
            }
        }

        for (int v : used[j]) {
            if (cw(x[i] - x[j], y[i] - y[j], x[j] - x[v], y[j] - y[v])) {
                good = false;
            }
        }

        if (good) {
            answer += sqrt(len);
        }

        used[i].push_back(j);
        used[j].push_back(i);
    }
    cout << fixed << setprecision(0) << answer << endl;
}