#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
using P = pair<int, int>;
using PL = pair<lint, lint>;
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
#define ALL(a)  (a).begin(),(a).end()
constexpr int MOD = 1000000007;
constexpr lint B1 = 1532834020;
constexpr lint M1 = 2147482409;
constexpr lint B2 = 1388622299;
constexpr lint M2 = 2147478017;
constexpr int INF = 2147483647;
void yes(bool expr) {cout << (expr ? "Yes" : "No") << "\n";}
template<class T>void chmax(T &a, const T &b) { if (a<b) a=b; }
template<class T>void chmin(T &a, const T &b) { if (b<a) a=b; }
struct Dist {lint d, u, v;};
int main()
{
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int N;
  cin >> N;
  vector<lint> x(N), y(N);
  REP(i, N) cin >> x[i] >> y[i];
  vector<Dist> d;
  REP(i, N) FOR(j, i+1, N) d.push_back(Dist{(x[i]-x[j])*(x[i]-x[j]) + (y[i]-y[j])*(y[i]-y[j]), i, j});
  sort(ALL(d), [](auto const &a, auto const &b) { return a.d < b.d; });
  vector<bool> existed(N, true);
  int ans = 0;
  REP(i, d.size()) {
    if(d[i].u == 0) {
      if(existed[d[i].v]) {
        ans++;
        existed[d[i].v] = false;
      }
    } else if(existed[d[i].u] && existed[d[i].v]){
      existed[d[i].u] = false;
      existed[d[i].v] = false;
    }
  }
  cout << ans << endl;
}