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

using namespace std;

int main(){

    vector<pair<long long, long long>> d;
    for (int i=-20; i<=20; i++){
        for (int j=-20; j<=20; j++) if (i*i+j*j<400) d.push_back({i, j});
    }

    long long N, X, Y, ans=0;
    cin >> N;
    set<pair<long long, long long>> st;

    for (int i=0; i<N; i++){
        cin >> X >> Y;
        bool f=1;
        for (auto [dx, dy] : d){
            if (st.count({X+dx, Y+dy})){
                f = 0;
                break;
            }
        }
        if (f){
            ans++;
            st.insert({X, Y});
        }
    }

    cout << ans << endl;

    return 0;
}