#include<bits/stdc++.h> #define pb push_back #define int long long #define S second #define F first #define inputt freopen("input.txt","r",stdin);freopen("outut.txt","w",stdout); #define ahah ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0); using namespace std; const int N=1e6+7; const int MOD=1e9+7; int x[N],y[N]; signed main() { ahah int n; cin >> n; for(int i = 1 ; i <= n ; i++){ cin >> x[i] >> y[i]; } int ans=0; for(int i = 1 ; i <= n ; i++){ for(int j = i+1 ; j <= n ; j++){ for(int k = j+1 ; k <= n ; k++){ set<int>xax; set<int>yax; xax.insert(x[i]); xax.insert(x[j]); xax.insert(x[k]); yax.insert(y[i]); yax.insert(y[j]); yax.insert(y[k]); if(xax.size() == 2 and yax.size() == 2){ ans++; } } } } cout << ans; }