#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define REP(i, n)           for(int(i)=0;(i)<(n);++(i))
#define FOR(i, f, t)        for(int(i)=(f);(i)<(t);(++i))
const int MOD = int(1e9+9);

bool f[22222][22222];
int c = 0;

int main(){
    int n;
    cin >> n;
    REP(i,n){
        int xx,yy;
        cin >> xx >> yy;
        bool b = true;
        for(int y = -19; y <= 19; y++){
            for(int x = -19; x <= 19; x++){
                int mx = xx + x, my = yy + y;
                if(mx < 0 || mx > 20000 || my < 0 || my > 20000) continue;
                if(f[my][mx] && (mx-xx)*(mx-xx)+(my-yy)*(my-yy) < 400){
                    b = false;
                }
            }
        }
        if(b) f[yy][xx] = true, c++;
    }
    cout << c << endl;
    return 0;
}