#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
#include <iostream>
#include <queue>
#include <list>
#include <map>
#include <numeric>
#include <set>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;


int main()
{
    int n;
    cin >> n;
    set<int> hash[20001];
    int ans = 0;
    int x;
    int y;
    for (int i = 0; i < n; i++)
    {
        cin >> x;
        cin >> y;
        bool canSet = true;
        for (int j = max(0, x - 19); j <= x + 19 && j <= 20000; j++)
        {
            if (hash[j].size() != 0)
            {
                for (int k = min(0, y - 19); k <= y + 19 && k <= 20000; k++)
                {
                    if (hash[j].find(k) != hash[j].end())
                    {
                        if ((x - j) * (x - j) + (y - k) * (y - k) < 400)
                        {
                            canSet = false;
                            j = x + 20 + 10;
                            k = y + 20 + 10;
                        }
                    }
                }
            }

        }
        if (canSet)
        {
            hash[x].insert(y);
            ans = ans + 1;
        }
    }
    cout << ans;
}