//SKD
// 16 32 108
#include<bits/stdc++.h>
#define ll long long int
#define pp push_back
#define pi 2*acos(0.0)
using namespace std;
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout<<fixed;
    cout<<setprecision(9);
    double m=0,p=0,l,q=0,r=0,t;
    int n,k,i,j;

        cin>>n;ll a[n],b[n];k=0;
        for(i=0; i<n; i++)cin>>a[i]>>b[i];
        for(i=0; i<n-1; i++)
        {
            for(j=i+1; j<n; j++)
            {
                l=b[j];q=b[i];t=a[i];r=a[j];
                p=(l-q)/(t-r);
                if(p>=-1 && p<=1)k++;
            }
        }
       cout<<k;
}


#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define R cin>>
#define ll long long
#define ln cout<<'\n'
#define in(a) insert(a)
#define pb(a) push_back(a)
#define pd(a) printf("%.10f\n",a)
#define mem(a) memset(a,0,sizeof(a))
#define all(c) (c).begin(),(c).end()
#define iter(c) __typeof((c).begin())
#define rrep(i,n) for(ll i=(ll)(n)-1;i>=0;i--)
#define REP(i,m,n) for(ll i=(ll)(m);i<(ll)(n);i++)
#define rep(i,n) REP(i,0,n)
#define tr(it,c) for(iter(c) it=(c).begin();it!=(c).end();it++)
ll check(ll n,ll m,ll x,ll y){return x>=0&&x<n&&y>=0&&y<m;}void pr(){ln;}
template<class A,class...B>void pr(const A &a,const B&...b){cout<<a<<(sizeof...(b)?" ":"");pr(b...);}
template<class A>void PR(A a,ll n){rep(i,n)cout<<(i?" ":"")<<a[i];ln;}
const ll MAX=1e9+7,MAXL=1LL<<61,dx[8]={-1,0,1,0,-1,-1,1,1},dy[8]={0,1,0,-1,-1,1,1,-1};
typedef pair<ll,ll> P;

void Main() {
  ll n;
  R n;
  P a[n];
  rep(i,n) cin >> a[i].F >> a[i].S;
  ll ans=0;
  rep(i,n) {
    REP(j,i+1,n) {
      ll x=abs(a[i].F-a[j].F),y=abs(a[i].S-a[j].S);
      if(x>=y) ans++;
    }
  }
  pr(ans);
}

int main(){ios::sync_with_stdio(0);cin.tie(0);Main();return 0;}
