/* -*- coding: utf-8 -*-
 *
 * 1265.cc:  No.1265 Balloon Survival - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 1000;
const int MAX_M = MAX_N * (MAX_N - 1) / 2;

/* typedef */

typedef long long ll;

struct Trpl {
  ll d;
  int i, j;
  Trpl() {}
  Trpl(ll _d, int _i, int _j): d(_d), i(_i), j(_j) {}

  bool operator<(const Trpl &t) const { return d < t.d; }

  void print() { printf("%lld:%d,%d\n", d, i, j); }
};

/* global variables */

int xs[MAX_N], ys[MAX_N];
Trpl ts[MAX_M];
bool used[MAX_N];

/* subroutines */

inline ll dist2(int i, int j) {
  int dx = xs[j] - xs[i], dy = ys[j] - ys[i];
  return (ll)dx * dx + (ll)dy * dy;
}

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d%d", xs + i, ys + i);

  int m = 0;
  for (int i = 0; i < n; i++)
    for (int j = i + 1; j < n; j++)
      ts[m++] = Trpl(dist2(i, j), i, j);
  sort(ts, ts + m);

  int c = 0;
  for (int k = 0; k < m; k++) {
    //ts[k].print();
    int i = ts[k].i, j = ts[k].j;
    if (i == 0) {
      if (! used[j]) used[j] = true, c++;
    }
    else {
      if (! used[i] && ! used[j])
	used[i] = used[j] = true;
    }
  }

  printf("%d\n", c);
  return 0;
}