#include<bits/stdc++.h>
using namespace std;
#define F                                               first
#define se                                              second
#define pb                                              push_back
#define SZ(x)                                           x.size()
#define all(v)		                                    ((v).begin()), ((v).end())
#define lp(i ,n)		                                for(int i=0;i<(int)(n);++i)
#define S(n) scanf("%d" , &n);
#define SL(n) scanf("%lld" , &n);
#define S2(n , m) scanf("%d %d" , &n , &m);
#define SL2(n , m) scanf("%lld %lld" , &n , &m);
#define dbg1(a)                                         std::cerr<<#a<<"= "<<(a)<<"\n"
#define dbg2(a,b)                                       std::cerr<<#a<<"= "<<(a)<<"  "<<#b<<"= "<<(b)<<"\n"
#define dbg3(a,b,c)                                     std::cerr<<#a<<"= "<<(a)<<"  "<<#b<<"= "<<(b)<<"  "<<#c<<"="<<(c)<<"\n"
#define dbg4(a,b,c,d)                                   std::cerr<<#a<<"= "<<(a)<<"  "<<#b<<"= "<<(b)<<"  "<<#c<<"="<<(c)<<" "<<#d<<"= "<<(d)<<"\n"
#define Fast ios_base::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL);


typedef long long LL;
int const N = 1e5+3;
int const mod = 1e9+7;
int dx[]= {-1, 1, 0, 0};
int dy[]= {0, 0, 1, -1};



int n ;
LL ans;
int main()
{

    S(n);

    vector<pair<double, double>>v(n);

    lp(i, n)scanf("%lf %lf",&v[i].F, &v[i].se);

    lp(i, n)
    {

        for(int j = i+1 ; j<n ; j++)

            ans += ((v[i].se - v[j].se) /(v[i].F - v[j].F)) >=-1 && ((v[i].se - v[j].se) /(v[i].F - v[j].F))<=1;


    }
    printf("%lld",ans);

    return 0;

}


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

#define ios ios_base::sync_with_stdio(0);cin.tie(nullptr);cout.tie(nullptr)
#define f first
#define s second
#define endl '\n'

typedef long long int ll ;

void solve() {
    int n ;
    cin >> n ;
    pair <double , double> xy[n] ;
    for (int i = 0 ; i < n ; i++) cin >> xy[i].f >> xy[i].s ;
    int ans = 0 ;
    for (int i = 0 ; i < n ; i++) {
        for (int j = i + 1; j < n ; j++) {
            double slope = xy[j].s - xy[i].s ;
            slope /= (xy[j].f - xy[i].f) ;
            if (slope >= -1 && slope <= 1) ans++ ;
        }
    }
    cout << ans << endl ;
}

int main() {
    ios ;
    
    solve() ;
}