#include <iostream>
#include <vector>
#include <cmath>
#include <map>
#include <set>
#include <iomanip>
#include <queue>
#include <algorithm>
#include <numeric>
#include <deque>
#include <complex>
#include <cassert>

using namespace std;

int main(){

    long long N, X, Y, mi, mx, d, cnt=0;
    cin >> N;
    vector<set<long long>> st(20001);

    for (int i=0; i<N; i++){
        cin >> X >> Y;
        bool f=1;
        mi = max(Y-20, 0LL);
        mx = min(Y+20, 20000LL);
        for (long long j=Y-20; j<=Y+20; j++){
            auto it = st[j].lower_bound(X-20);
            auto it2 = st[j].lower_bound(X+20);
            for (auto k=it; k!=it2; k++){
                d = (j-Y)*(j-Y) + (*k-X)*(*k-X);
                if (d < 400){
                    f = 0;
                    break;
                }
            }
            if (!f) break;
        }
        if (f){
            st[Y].insert(X);
            cnt++;
        }
    }

    cout << cnt << endl;

    return 0;
}