#include "bits/stdc++.h"
using namespace std;

#define REP(i, n) for(int i=0; i<(n); i++)
struct P { int x, y; P(){}; P(int _x, int _y): x(_x), y(_y){}; };

int N,T;
vector<int> M[1111][1111];
vector<P> ps;
int distance2(P a, P b) {
    return pow(a.x - b.x, 2) + pow(a.y - b.y, 2);
}
signed main()
{
    cin >> N;
    int ans = 0;
    int x,y;
    REP(i,N) {
        cin >> x >> y;
        ps.push_back(P(x, y));
        int mx = ps[i].x / 20;
        int my = ps[i].y / 20;
        int dxy9[] = {-1, 0, 1};
        bool ok = true;
        REP(k,9) {
            int nx = mx + dxy9[k/3];
            int ny = my + dxy9[k%3];
            if (nx<0||ny<0) continue;
            for (auto&& j : M[nx][ny]) {
                if (distance2(ps[j], ps[i]) < 400) {
                    // conflict
                    ok = false;
                    break;
                }
            }
            if (!ok) break;
        }
        if (ok) {
            M[mx][my].push_back(i);
            ans++;
        }
    }
    cout << ans << endl;
    return 0;
}