#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <cmath>
#include <iomanip>
#include <map>
using namespace std;
typedef long long LL;

char board[20001][20001];

void place(int sy, int sx){
    for(LL y = sy - 20; y <= sy + 20; y++){
        if(y < 0 || 20000 < y) continue;
        for(LL x = sx - 20; x <= sx + 20; x++){
            if(x < 0 || 20000 < x) continue;
            if((x-sx)*(x-sx) + (y-sy)*(y-sy) >= 400) continue;
            board[y][x] = 1;
        }
    }
}

int main(){
    LL N;
    cin >> N;
    LL ans = 0;
    for(int i = 0; i < N; i++){
        int x, y;
        cin >> x >> y;
        if(board[y][x] == 0){
            place(y, x);
            ans++;
        }
    }
    cout << ans << endl;
    return 0;
}