#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <set>
#include <map>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
#define loop(i,a,b) for(int i=(a);i<int(b);i++)
#define rep(i,b) loop(i,0,b)
#define all(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;

//#define int ll
//#define endl "\n"

template<typename Type, unsigned N, unsigned Last>
struct tuple_printer
{
    static void print(std::ostream& out, const Type& value)
    {
        out << std::get<N>(value) << ", ";
        tuple_printer<Type, N + 1, Last>::print(out, value);
    }
};
template<typename Type, unsigned N>
struct tuple_printer < Type, N, N >
{
    static void print(std::ostream& out, const Type& value)
    {
        out << std::get<N>(value);
    }
};
template<typename... Types>
std::ostream& operator<<(std::ostream& out, const std::tuple<Types...>& value)
{
    out << "(";
    tuple_printer<std::tuple<Types...>, 0, sizeof...(Types)-1>::print(out, value);
    out << ")";
    return out;
}

#ifdef DEBUG
#define dump(...) (cerr << #__VA_ARGS__ << " = " << make_tuple(__VA_ARGS__) << " [" << __LINE__ << "]" << endl)
#else
#define dump(...)
#endif

int main(){
    int n;
    cin >> n;
    vector<pair<int, int>> cur;
    rep(i, n){
        int x, y;
        cin >> x >> y;
        auto put = make_pair(x, y);
        bool hit = false;
        for (auto & p : cur){
            int dx = p.first - x;
            int dy = p.second - y;
            dump(dx, dy);
            if (dx*dx + dy*dy >= 400) continue;
            hit = true;
            break;
        }
        dump(hit);
        if (!hit){
            cur.push_back(put);
        }
    }
    cout << cur.size() << endl;
}