#include <bits/stdc++.h>
#define int long long
using namespace std;

const int N = 2e3 + 5;
const int Mod = 998244353;

int xx, yy;
bool vis[N];

struct dot{
	int x, y, id, idx;
}d[N], e[N], stac[N];

int cross(dot a, dot b, dot c) // ������ 
{
	return (b.x - a.x) * (c.y - a.y) - (c.x - a.x) * (b.y - a.y);
}

bool cmp2(dot a, dot b)
{
	if (atan2(a.y - yy, a.x - xx) != atan2(b.y - yy, b.x - xx)) {
		return atan2(a.y - yy, a.x - xx) < atan2(b.y - yy, b.x - xx);
	}
	return a.x < b.x;
}

bool cmp1(dot a, dot b)
{
	return (a.y == b.y) ? (a.x < b.x) : (a.y < b.y);
}

signed main()
{
	std::ios::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	int n, top = 0, ans = 1;
	cin >> n;
	for (int i = 1; i <= n; ++i) {
		cin >> d[i].x >> d[i].y;
	}
	sort(d + 1, d + n + 1, cmp1);
	stac[++top] = {d[1].x, d[1].y, 1, 1};
	vis[1] = 1;
	xx = d[1].x; yy = d[1].y;
	sort(d + 2, d + n + 1, cmp2);
	stac[++top] = {d[2].x, d[2].y, 2, 2};
	vis[2] = 1;
	for (int i = 1; i <= n; ++i) {
		e[i] = {d[i].x, d[i].y, i, i};
	}
	for (int i = 3; i <= n; ++i) {
		while (top >= 2 && cross(d[stac[top - 1].id], d[stac[top].id], d[i]) < 0) {
			vis[stac[top].id] = 0;
			--top;
		}
		stac[++top] = {d[i].x, d[i].y, i, top};
		vis[stac[top].id] = 1;
	}
	for (int i = 1; i <= n; ++i) {
		if (vis[i]) continue;
		xx = d[i].x; yy = d[i].y;
		sort(e + 1, e + n + 1, cmp2);
		/*cout << xx << " , " << yy << "&&\n";
		for (int j = 1; j <= n; ++j) {
			cout << j  << "(" << e[j].x << ", " << e[j].y << ") :" << atan2(e[j].y - yy, e[j].x - xx) << "##\n";
		}*/
		for (int j = 1; j < n; ++j) {
		//	cout << atan2(stac[j].y - yy, stac[j].x - xx) << " * " << atan2(stac[j + 1].y - yy, stac[j + 1].x - xx) << "\n";
		//	int res = abs(e[j].idx - e[j + 1].idx);
			if (e[j].id == i) continue;
			if (vis[e[j].idx] && (vis[e[j + 1].idx] || (e[j + 1].id == i && vis[e[j + 2].id]))) {
				++ans;
			/*	cout << "(" << e[j].x << ", " << e[j].y << ") - ";
				cout << "(" << d[i].x << ", " << d[i].y << ") - ";
				cout << "(" << e[j + 1].x << ", " << e[j + 1].y << ")\n";*/
			}
		}
		if (e[1].id == i) {
			if (vis[e[2].id] && vis[e[n].id]) ++ans;
		}
		else if (e[n].id == i) {
			if (vis[e[1].id] && vis[e[n - 1].id]) ++ans;
		}
		else {
			if (vis[e[1].id] && vis[e[n].id]) ++ans;
		}
	}
	cout << ans;
	return 0;
}