#include <iostream>
#include <algorithm>
#include <iomanip>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <cmath>
#include <limits>


static const int MOD = 1000000007;
using ll = long long;
using u32 = uint32_t;
using namespace std;

template<class T> constexpr T INF = ::numeric_limits<T>::max() / 32 * 15 + 208;

template <class T, class U>
vector<T> make_v(U size, const T& init){ return vector<T>(static_cast<size_t>(size), init); }

template<class... Ts, class U>
auto make_v(U size, Ts... rest) { return vector<decltype(make_v(rest...))>(static_cast<size_t>(size), make_v(rest...)); }

template<class T> void chmin(T &a, const T &b){ a = (a < b ? a : b); }
template<class T> void chmax(T &a, const T &b){ a = (a > b ? a : b); }

int main() {
    auto dp = make_v(5004, 5004, make_pair(-1, -1));
    int n;
    cin >> n;
    pair<int, int> D = {-1, -1};
    int ans = 0;
    for (int i = 0; i < n; ++i) {
        int x, y;
        cin >> x >> y;
        int ok = 1;
        int xx = x/10+2, yy = y/10+2;
        for (int dx = -2; dx <= 2; ++dx) {
            for (int dy = -2; dy <= 2; ++dy) {
                if(dp[xx+dx][yy+dy] != D){
                    int px, py;
                    tie(px, py) = dp[xx+dx][yy+dy];
                    if((px-x)*(px-x)+(py-y)*(py-y) < 400){
                        ok = 0;
                        dx = 3, dy = 3;
                        break;
                    }
                }
            }
        }
        if(ok) ans++, dp[xx][yy] = {x, y};
    }
    cout << ans << "\n";
    return 0;
}