#include <bits/stdc++.h>
using namespace std;
#define int long long
const double pi = acos(-1);
int n, vis[2010];
pair<int, int> a[2010];
double val[2010];
int calc(pair<int, int> i, pair<int, int> j, pair<int, int> k) {
	return (j.first - i.first) * (k.second - i.second) - (j.second - i.second) * (k.first - i.first);
}
signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0), cout.tie(0);
	cin >> n;
	for (int i = 1; i <= n; i++)
		cin >> a[i].first >> a[i].second;
	sort(a + 1, a + n + 1);
	vector<int> u, d, p;
	u.push_back(1), d.push_back(1);
	for (int i = 2; i <= n; i++) {
		while (u.size() > 1) {
			int j = u.back(), k = u[u.size() - 2];
			if (calc(a[k], a[j], a[i]) > 0) u.pop_back();
			else break;
		}
		u.push_back(i);
		while (d.size() > 1) {
			int j = d.back(), k = d[d.size() - 2];
			if (calc(a[k], a[j], a[i]) < 0) d.pop_back();
			else break;
		}
		d.push_back(i);
	}
	for (int x : u) vis[x] = 1;
	for (int x : d) vis[x] = 1;
	for (int i = 1; i <= n; i++)
		if (!vis[i]) p.push_back(i);
	int ans = 1;
	for (int i = 1; i < d.size(); i++) {
		int o = d[i - 1], v = d[i];
		double t = atan2(a[v].second - a[o].second, a[v].first - a[o].first);
		for (int x : p) {
			val[x] = atan2(a[x].second - a[o].second, a[x].first - a[o].first);
			val[x] -= t;
			if (val[x] < 0) val[x] += pi * 2;
		}
		sort(p.begin(), p.end(), [&](int x, int y) {
			return val[x] > val[y];
		});
		stack<int> st;
		for (int x : p) {
			while (!st.empty()) {
				int y = st.top();
				if (calc(a[o], a[y], a[x]) > 0 && calc(a[v], a[x], a[y]) > 0)
					st.pop();
				else break;
			}
			if (!st.empty()) {
				int y = st.top();
				if (calc(a[o], a[x], a[y]) > 0 && calc(a[v], a[y], a[x]) > 0)
					continue;
			}
			st.push(x);
		}
		ans += st.size();
	}
	for (int i = 1; i < u.size(); i++) {
		int o = u[i], v = u[i - 1];
		double t = atan2(a[v].second - a[o].second, a[v].first - a[o].first);
		for (int x : p) {
			val[x] = atan2(a[x].second - a[o].second, a[x].first - a[o].first);
			val[x] -= t;
			if (val[x] < 0) val[x] += pi * 2;
		}
		sort(p.begin(), p.end(), [&](int x, int y) {
			return val[x] > val[y];
		});
		stack<int> st;
		for (int x : p) {
			while (!st.empty()) {
				int y = st.top();
				if (calc(a[o], a[y], a[x]) > 0 && calc(a[v], a[x], a[y]) > 0)
					st.pop();
				else break;
			}
			if (!st.empty()) {
				int y = st.top();
				if (calc(a[o], a[x], a[y]) > 0 && calc(a[v], a[y], a[x]) > 0)
					continue;
			}
			st.push(x);
		}
		ans += st.size();
	}
	cout << ans << endl;
	return 0;
}