#define MOD_TYPE 1

#pragma region Macros
#include <bits/stdc++.h>
using namespace std;

#if 0
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/multiprecision/cpp_dec_float.hpp>
using Int = boost::multiprecision::cpp_int;
using lld = boost::multiprecision::cpp_dec_float_100;
#endif
#if 1
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#endif
using ll = long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;
template <typename Q_type>
using smaller_queue = priority_queue<Q_type, vector<Q_type>, greater<Q_type>>;

constexpr ll MOD = (MOD_TYPE == 1 ? (ll)(1e9 + 7) : 998244353);
//constexpr ll MOD = 1;
constexpr int INF = (int)1e9 + 10;
constexpr ll LINF = (ll)4e18;
constexpr double PI = acos(-1.0);
constexpr double EPS = 1e-11;
constexpr int Dx[] = {0, 0, -1, 1, -1, 1, -1, 1, 0};
constexpr int Dy[] = {1, -1, 0, 0, -1, -1, 1, 1, 0};

#define REP(i, m, n) for (ll i = m; i < (ll)(n); ++i)
#define rep(i, n) REP(i, 0, n)
#define REPI(i, m, n) for (int i = m; i < (int)(n); ++i)
#define repi(i, n) REPI(i, 0, n)
#define MP make_pair
#define MT make_tuple
#define YES(n) cout << ((n) ? "YES" : "NO") << "\n"
#define Yes(n) cout << ((n) ? "Yes" : "No") << "\n"
#define possible(n) cout << ((n) ? "possible" : "impossible") << "\n"
#define Possible(n) cout << ((n) ? "Possible" : "Impossible") << "\n"
#define Yay(n) cout << ((n) ? "Yay!" : ":(") << "\n"
#define all(v) v.begin(), v.end()
#define NP(v) next_permutation(all(v))
#define dbg(x) cerr << #x << ":" << x << "\n";

struct io_init
{
  io_init()
  {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << setprecision(30) << setiosflags(ios::fixed);
  };
} io_init;
template <typename T>
inline bool chmin(T &a, T b)
{
  if (a > b)
  {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
inline bool chmax(T &a, T b)
{
  if (a < b)
  {
    a = b;
    return true;
  }
  return false;
}
inline ll CEIL(ll a, ll b)
{
  return (a + b - 1) / b;
}
template <typename A, size_t N, typename T>
inline void Fill(A (&array)[N], const T &val)
{
  fill((T *)array, (T *)(array + N), val);
}
template <typename T, typename U>
constexpr istream &operator>>(istream &is, pair<T, U> &p) noexcept
{
  is >> p.first >> p.second;
  return is;
}
template <typename T, typename U>
constexpr ostream &operator<<(ostream &os, pair<T, U> &p) noexcept
{
  os << p.first << " " << p.second;
  return os;
}
#pragma endregion

void validate(int &n, vector<ll> &x, vector<ll> &y)
{
  assert(cin >> n);
  assert(1 <= n and n <= 1000);
  x.resize(n);
  y.resize(n);
  rep(i, n) assert(cin >> x[i] >> y[i]);
  string temp;
  assert(!(cin >> temp));
  for (auto t : x)
    assert(abs(t) <= 1e8);
  for (auto t : y)
    assert(abs(t) <= 1e8);
  rep(i, n) REP(j, i + 1, n)
  {
    assert(x[i] != x[j] or y[i] != y[j]);
  }

  vector<vector<ll>> d(n, vector<ll>(n));
  rep(i, n) REP(j, i + 1, n)
  {
    d[i][j] = d[j][i] = (x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]);
  }
  // どの3つの風船も同時に接触しない
  rep(i, n) REP(j, i + 1, n) REP(k, j + 1, n)
  {
    assert(!(d[i][j] == d[i][k] and d[i][j] <= d[j][k]));
    assert(!(d[j][i] == d[j][k] and d[j][i] <= d[i][k]));
    assert(!(d[k][i] == d[k][j] and d[k][i] <= d[i][j]));
  }
}

void solve()
{
  int n;
  vector<ll> x, y;
  validate(n, x, y);

  vector<tuple<ll, int, int>> v;
  rep(i, n) REP(j, i + 1, n)
  {
    ll d = (x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]);
    v.push_back({d, i, j});
  }
  sort(all(v));
  vector<bool> used(n, false);
  int cnt = 0;
  for (auto [d, i, j] : v)
  {
    if (used[i] or used[j])
      continue;
    if (i == 0)
      used[j] = true, cnt++;
    else if (j == 0)
      used[i] = true, cnt++;
    else
      used[i] = used[j] = true;
  }
  cout << cnt << "\n";
}

int main()
{
  solve();
}