#include <iostream>
#include <string>
#include <vector>
#include <functional>
#include <algorithm>
#include <cmath>

#define REP(i,n) for(int i=0;i<(n);i++)

using namespace std;

bool is_on(pair<int,int> &a, pair<int, int> &b)
{
    double dist = (a.first - b.first) * (a.first - b.first) + (a.second - b.second) * (a.second - b.second);
    dist = sqrt(dist);
    return dist < 20;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int N;
    cin >> N;
    int x, y;
    cin >> x >> y;
    N--;
    vector<pair<int, int> > coins;
    coins.emplace_back(x, y);

    REP(i, N) {
        cin >> x >> y;
        auto p = pair<int,int>(x, y);
        if (!any_of(coins.begin(), coins.end(), [&p](pair<int, int> &a) { return is_on(a, p); })) {
            coins.push_back(move(p));
        }
    }
    cout << coins.size() << endl;

    return 0;
}