#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef pair<ll, ll> p_ll;

template<class T>
void debug(T itr1, T itr2) { auto now = itr1; while(now<itr2) { cout << *now << " "; now++; } cout << endl; }
#define repr(i,from,to) for (ll i=(ll)from; i<(ll)to; i++)
#define all(vec) vec.begin(), vec.end()
#define rep(i,N) repr(i,0,N)
#define per(i,N) for (int i=(int)N-1; i>=0; i--)

const ll MOD = pow(10,9)+7;
const ll LLINF = pow(2,61)-1;
const int INF = pow(2,30)-1;

vector<ll> fac;
void c_fac(int x=pow(10,6)+10) { fac.resize(x,true); rep(i,x) fac[i] = i ? (fac[i-1]*i)%MOD : 1; }
ll modpow(ll x, ll p) { ll result = 1, now = 1, pm = x; while (now<=p) { if (p&now) { result = result * pm % MOD; } now*=2; pm = pm*pm % MOD; } return result; }
ll inv(ll a, ll m=MOD) { ll b = m, x = 1, y = 0; while (b!=0) { int d = a/b; a -= b*d; swap(a,b); x -= y*d; swap(x,y); } return (x+m)%m; }
ll nck(ll n, ll k) { return fac[n]*inv(fac[k]*fac[n-k]%MOD)%MOD; }
ll gcd(ll a, ll b) { if (a<b) swap(a,b); return b==0 ? a : gcd(b, a%b); }
ll lcm(ll a, ll b) { return a/gcd(a,b)*b; }

struct baloon { ll x, y; };
struct bpair { 
  ll i, j, d;
  bool operator< (const bpair &b) const { return d<b.d||(d==b.d&&(i<b.i||(i==b.i&&j<b.j))); };
};

int main() {
  ll N; cin >> N;
  baloon b[N]; rep(i,N) cin >> b[i].x >> b[i].y;
  set<bpair> bp;
  rep(i,N) repr(j,i+1,N) {
    ll d = pow(b[i].x-b[j].x,2) + pow(b[i].y-b[j].y,2);
    bp.insert((bpair){i,j,d});
  }

  bool used[N] = {};
  ll result = 0;
  for (auto x: bp) {
    // cout << x.i << "-" << x.j << ":" << x.d << endl;
    if (used[x.i]||used[x.j]) continue;
    if (x.i==0) { result++; used[x.j] = true; }
    else { used[x.i] = true; used[x.j] = true; }
  }
  cout << result << endl;
  return 0;
}