#include <bits/stdc++.h>
using namespace std;
#define TRACE(x) cerr << #x << " = " << x << endl
#define _ << " _ " <<
#define fi first
#define se second
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef vector<int> vi;
int sign(ll x) {
if (x > 0) return 1;
if (x < 0) return -1;
return 0;
}
int ccw(const pii& a, const pii& b, const pii& c) {
return sign((ll)a.fi * (b.se - c.se) +
(ll)b.fi * (c.se - a.se) +
(ll)c.fi * (a.se - b.se));
}
bool intersect(const pii& a, const pii& b, const pii& c, const pii& d) {
if (a == b || a == c || a == d || b == c || b == d || c == d) return false;
return ccw(a, b, c) != ccw(a, b, d) && ccw(c, d, a) != ccw(c, d, b);
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int n;
cin >> n;
vector<pii> pts(n);
for (auto& it : pts) cin >> it.fi >> it.se;
int sol = 0;
vector<pair<pii, pii>> tr;
for (auto& a : pts) for (auto& b : pts) {
if (a == b) continue;
bool ok = true;
for (auto& it : tr)
ok &= !intersect(a, b, it.fi, it.se) && (it != make_pair(b, a));
if (!ok) continue;
tr.push_back({a, b});
for (auto& c : pts) for (auto& d : pts)
ok &= !intersect(a, b, c, d);
sol += ok;
}
cout << sol << '\n';
return 0;
}
