#include <bits/stdc++.h>
using namespace std;
#define all(a) a.begin(), a.end()
void print() { cout << '\n'; }
template <typename T, typename...Args>
void print(T t, Args...args) { cout << t << ' '; print(args...); }
using ll = long long;
const int N = 50005;

using T = ll;

const T pi = acos(-1);

using Point = array<T, 2>;

Point operator - (const Point a, const Point b) {
    auto [x1, y1] = a;
    auto [x2, y2] = b;
    return {x1 - x2, y1 - y2};
}

T cross (Point a, Point b) {
    auto [x1, y1] = a;
    auto [x2, y2] = b;
    return x1 * y2 - x2 * y1;
}

T dis (Point& a, Point& b) {
    return sqrt((a[0] - b[0]) * (a[0] - b[0]) + (a[1] - b[1]) * (a[1] - b[1]));
}

vector<int> get_convex_hull (vector<Point> p) {
    int n = p.size();
    vector<int> stk(n + 1);
    int top = -1;
    for (int i = 0; i < n; i ++) {
        while (top >= 1 && cross(p[stk[top]] - p[stk[top - 1]], p[i] - p[stk[top - 1]]) <= 0) {
            top --;
        }
        stk[++ top] = i;
    }
    int t = top;
    for (int i = n - 2; i >= 0; i --) {
        while (top > t && cross(p[stk[top]] - p[stk[top - 1]], p[i] - p[stk[top - 1]]) <= 0) {
            top --;
        }
        stk[++ top] = i;
    }
    stk.resize(top + 1);
    return stk;
}

int sign (Point p) {
    auto [x, y] = p;
    return x > 0 || x == 0 && y > 0;
}

void solve () {
    int n;
    cin >> n;

    vector<Point> a(n);
    for (auto& [x, y]: a) {
        cin >> x >> y;
    }

    sort(all(a));

    auto convex = get_convex_hull(a);

    vector<int> on_convex(n);
    for (auto& i: convex) {
        on_convex[i] = 1;
    }

    int ans = 1;
    for (int i = 0; i < n; i ++) {
        if (!on_convex[i]) {
            vector<int> p;
            for (int j = 0; j < n; j ++) {
                if (j != i) {
                    p.push_back(j);
                }
            }
            sort(all(p), 
                [&](int x, int y) {
                    if (sign(a[x]) != sign(a[y])) {
                        return sign(a[x]) < sign(a[y]);
                    }
                    return cross(a[x] - a[i], a[y] - a[i]) > 0;
                });
            int m = p.size();
            for (int x = 0; x < m; x ++) {
                ans += on_convex[p[x]] && on_convex[p[(x + 1) % m]];
            }
        }
    }
    cout << ans << '\n';
}

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	
	int t = 1;
    // cin >> t;
    while (t --) {
        solve();
    }

	return 0;
}