#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef int64_t lint;
#define rep(i, n) for(int i=0; i<n; i++)
#define repx(i, l, n) for(int i=l; i<n; i++)
#define all(v) v.begin(), v.end()
#define show(x) cout << #x << ": " << x << endl;
#define list(x) cout << #x << ": " << x << "  ";
#define pb push_back
using vi = vector<lint>;
using vvi = vector<vector<lint>>;
template<class T> inline void vin(vector<T>& v) { rep(i, v.size()) cin >> v.at(i); }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T> inline void drop(T x) { cout << x << endl; exit(0); }
template<class T> void vout(vector<T> v) { rep(i, v.size()) { cout << v.at(i) << ' '; } cout << endl; }
constexpr lint LINF = LLONG_MAX/2;
using pint = pair<lint, lint>;
using vp = vector<pint>;
map<pint, lint> polar_sort(vp &v) {
	sort(all(v), [](auto const& lhs, auto const& rhs) {
		return lhs.first*rhs.second < rhs.first*lhs.second;
	});
	map<pint, lint> m;
	lint a = 0;
	for (auto p : v) m[p] = ++a;
	return m;
}

int main() {
	lint N;
	cin >> N;
	vp v(N);

	lint a=0, b=0, c=0, x, y, z;
	rep(i, N) {
		cin >> x >> y;
		v[i] = {x, y};
	}
	rep(i, N) {
		vp w;
		rep(j, N) {
			if (i == j) continue;
			w.pb({v[j].first-v[i].first, v[j].second-v[i].second});
		}
		map<pint, lint> m = polar_sort(w);
		rep(j, N-2) {
			if (w[j].first*w[j+1].second == w[j].second*w[j+1].first) {
				a++;
				break;
			}
		}
	}
	std::cout << a << '\n';
}