#include "bits/stdc++.h"

using namespace std;

int main(){
    int n;cin>>n;
    vector<pair<int, int>> v;
    for(int i=0;i<n;i++){
        int a,b;cin>>a>>b;
        v.push_back(make_pair(a,b));
    }
    int count=0;
    float slopey;
    float slopex;
    for(int j=0;j<v.size();j++){
        for(int i=j+1;i<v.size();i++){
            slopey = (v[j].second-v[i].second);
            slopex = (v[j].first-v[i].first);
            float slope = slopey/slopex;
            if(slope<=1&&slope>=-1) count++;
        }
    }
    cout<<count;
}
#include <bits/stdc++.h>

using namespace std;

#define REP(i, n) for (int i=0; i<(n); ++i)
#define RREP(i, n) for (int i=(int)(n)-1; i>=0; --i)
#define FOR(i, a, n) for (int i=(a); i<(n); ++i)
#define RFOR(i, a, n) for (int i=(int)(n)-1; i>=(a); --i)

#define SZ(x) ((int)(x).size())
#define ALL(x) (x).begin(),(x).end()

#define DUMP(x) cerr<<#x<<" = "<<(x)<<endl
#define DEBUG(x) cerr<<#x<<" = "<<(x)<<" (L"<<__LINE__<<")"<<endl;

template<class T>
ostream &operator<<(ostream &os, const vector <T> &v) {
    os << "[";
    REP(i, SZ(v)) {
        if (i) os << ", ";
        os << v[i];
    }
    return os << "]";
}

template<class T, class U>
ostream &operator<<(ostream &os, const pair <T, U> &p) {
    return os << "(" << p.first << " " << p.second << ")";
}

template<class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template<class T>
bool chmin(T &a, const T &b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}

using ll = long long;
using ull = unsigned long long;
using ld = long double;
using P = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;
using vvi = vector<vi>;
using vvll = vector<vll>;

const ll MOD = 1e9 + 7;
const int INF = INT_MAX / 2;
const ll LINF = LLONG_MAX / 2;
const ld eps = 1e-9;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);

    int n; cin >> n;
    vi x(n), y(n);
    REP(i, n) cin >> x[i] >> y[i];

    int ans = 0;
    REP(i, n) {
        for (int j = i+1; j < n; ++j) {
            if (abs(y[i] - y[j]) <= abs(x[i] - x[j])) {
                ++ans;
            }
        }
    }
    cout << ans << endl;

    return 0;
}