#include <iostream>
#include <vector>

using namespace std;

int main()
{
  int N;
  cin >> N;
  vector<pair<int, int>> v(N);
  for (int i = 0; i < N; ++i) {
    cin >> v[i].first >> v[i].second;
  }
  int ans = 0;
  for (int i = 0; i < N; ++i) {
    for (int j = i + 1; j < N; ++j) {
      if (abs(v[i].first - v[j].first) >= abs(v[i].second - v[j].second)) {
        ++ans;
      }
    }
  }
  cout << ans << endl;
  return 0;
}
#include<bits/stdc++.h>
using namespace std;
#define gc getchar_unlocked
#define fo(i,n) for(i=0;i<n;i++)
#define Fo(i,k,n) for(i=k;k<n?i<n:i>n;k<n?i+=1:i-=1)
#define rArr(v) for(auto &i: v) cin >> i
#define pArr(v) for(auto i: v) cout << i << " "
#define ll long long
#define si(x)	scanf("%d",&x)
#define sl(x)	scanf("%lld",&x)
#define ss(s)	scanf("%s",s)
#define pi(x)	printf("%d\n",x)
#define pl(x)	printf("%lld\n",x)
#define ps(s)	printf("%s\n",s)
#define deb(x) cout << #x << "=" << x << endl
#define deb2(x, y) cout << #x << "=" << x << "," << #y << "=" << y << endl
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define clr(x) memset(x, 0, sizeof(x))
#define sortall(x) sort(all(x))
#define tr(it, a) for(auto it = a.begin(); it != a.end(); it++)
#define PI 3.1415926535897932384626
typedef pair<int, int>	pii;
typedef pair<ll, ll>	pl;
typedef vector<int>		vi;
typedef vector<ll>		vl;
typedef vector<pii>		vpii;
typedef vector<pl>		vpl;
typedef vector<vi>		vvi;
typedef vector<vl>		vvl;
mt19937_64 rang(chrono::high_resolution_clock::now().time_since_epoch().count());
int rng(int lim) {
	uniform_int_distribution<int> uid(0,lim-1);
	return uid(rang);
}
int mpow(int base, int exp); 
void ipgraph(int n, int m);
void dfs(int u, int par);

const int mod = 1'000'000'007;
const int N = 3e5, M = N;
//=======================

vi g[N];
int a[N];

void solve() {
  int i, j, n, m;
  cin >> n;
  vpii points(n, {0, 0});

  for(pii &point: points) {
    cin >> point.F >> point.S;
  }

  int counter = 0;

  for(i = 0; i<n; i++) {
    for(j = i + 1; j<n; j++) {
      float slope = float(points[j].S - points[i].S)/float(points[j].F - points[i].F);
      // deb(slope);
      if(slope >= -1 && slope <= 1) counter++;
    }
  }

  cout << counter << endl;

}

int main() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    srand(chrono::high_resolution_clock::now().time_since_epoch().count());

    int t = 1;
    // cin >> t;
    while(t--) {
      solve();
    }

    return 0;
}

int mpow(int base, int exp) {
  base %= mod;
  int result = 1;
  while (exp > 0) {
    if (exp & 1) result = ((ll)result * base) % mod;
    base = ((ll)base * base) % mod;
    exp >>= 1;
  }
  return result;
}

void ipgraph(int n, int m){
	int i, u, v;
	while(m--){
		cin>>u>>v;
    u--, v--;
		g[u].pb(v);
		g[v].pb(u);
	}
}

void dfs(int u, int par){
	for(int v:g[u]){
		if (v == par) continue;
		dfs(v, u);
	}
}