#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define MASK(x) (1LL << (x))
#define BIT(x, i) (((x) >> (i)) & 1)
#define SZ(x) ((int) (x).size())
#define ALL(a) (a).begin(), (a).end()
#define FOR(i, a, b) for (int i = (a); i <= (b); ++i)
#define FORD(i, a, b) for (int i = (a); i >= (b); --i)
#define debug(x) cerr << "[" << #x << " = " << (x) << "]" << endl
#define left __left
#define right __right
#define prev __prev
#define fi first
#define se second
template <class X, class Y>
bool maximize(X &x, Y y) {
if (x < y) return x = y, true;
else return false;
}
template <class X, class Y>
bool minimize(X &x, Y y) {
if (x > y) return x = y, true;
else return false;
}
int n;
#define MAX_POINT 1'010
struct Point {
ll x, y;
Point(ll _x = 0, ll _y = 0) {
x = _x, y = _y;
}
void input() {
cin >> x >> y;
}
Point operator - (const Point &other) const {
return Point(x - other.x, y - other.y);
}
} p[MAX_POINT + 2];
using Vecto = Point;
ll dot(Vecto A, Vecto B) {
return A.x * B.x + A.y * B.y;
}
ll cross(Vecto A, Vecto B) {
return A.x * B.y - A.y * B.x;
}
ll cross(Point A, Point B, Point C) {
Vecto AB = B - A, AC = C - A;
return cross(AB, AC);
}
int sign(ll x) {
return (x > 0 ? 1 : (x == 0 ? 0 : -1));
}
struct Line {
Point a, b;
};
// AB . AC = |AB| * |AC| * cos(AB, AC)
bool inside(Point A, Point B, Point C) { // C in segment AB;
Vecto CA = A - C, CB = B - C;
return (dot(CA, CB) <= 0 && cross(CA, CB) == 0);
// dot(CA, CB) == 0 khi C trungf A or C trungf B;
// dot(CA, CB) < 0 ==> dot(CA, CB) == 1 ==> C nam giua A va B;
}
bool intersect(Line X, Line Y) {
if (inside(X.a, X.b, Y.a)) return false;
if (inside(X.a, X.b, Y.b)) return false;
if (inside(Y.a, Y.b, X.a)) return false;
if (inside(Y.a, Y.b, X.b)) return false;
int direct_one = sign(cross(X.a, X.b, Y.a));
int direct_two = sign(cross(X.a, X.b, Y.b));
int direct_three = sign(cross(Y.a, Y.b, X.a));
int direct_four = sign(cross(Y.a, Y.b, X.b));
return (direct_one * direct_two < 0 && direct_three * direct_four < 0);
}
namespace subtask1 {
bool check() {
return (n <= 40);
}
Line arr[100000];
bool ok[100000];
void solve() {
int cur = 0;
FOR(i, 1, n) {
FOR(j, i + 1, n) {
arr[++cur] = {p[i], p[j]};
}
}
memset(ok, true, sizeof(ok));
FOR(i, 1, cur) {
FOR(j, i + 1, cur) if (intersect(arr[i], arr[j])) {
ok[i] = false;
ok[j] = false;
}
}
int ans = 0;
FOR(i, 1, cur) ans += ok[i];
cout << ans;
}
}
int main() {
ios_base::sync_with_stdio(false);cin.tie(nullptr);
#define task ""
if (fopen(task".inp","r")) {
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
cin >> n;
FOR(i, 1, n) p[i].input();
if (subtask1 :: check()) return subtask1 :: solve(), 0;
subtask1 :: solve();
return 0;
}
/* Discipline - Calm */
