#include <bits/stdc++.h>

using namespace std;

template<typename T> inline T gcd(T a, T b) {
  return __gcd(a, b);
}

template<typename T> inline T lcm(T a, T b) {
  return a / gcd(a, b) * b;
}

template<typename T> inline T floor(T a, T b) {
  return floor(a / b) * b <= a ? floor(a / b) : floor(a / b) - 1;
}

template<typename T> inline T ceil(T a, T b) {
  return floor(a + b - 1, b);
}

template<typename T> inline T round(T a, T b) {
  return floor(a + b / 2);
}

template<typename T> inline T mod(T a, T b) {
  return a - floor(a, b) * b;
}

template<typename T> inline T factorial(T n) {
  return n <= 1 ? 1 : factorial(n - 1) * n;
}

int main() {
  int n;
  cin >> n;
  map<pair<int, int>, vector<pair<int, int>>> c;
  int res = 0;
  for (int i = 0; i < n; ++i) {
    int x, y;
    cin >> x >> y;
    int a = floor(x, 20), b = floor(y, 20);
    bool ok = true;
    for (int i = a - 1; i <= a + 1; ++i) {
      for (int j = b - 1; j <= b + 1; ++j) {
        for (auto k : c[make_pair(i, j)]) {
          if (pow(x - k.first, 2) + pow(y - k.second, 2) < 400) ok = false;
        }
      }
    }
    if (ok) {
      c[make_pair(a, b)].emplace_back(make_pair(x, y));
      ++res;
    }
  }
  cout << res << endl;
}