#include <cstdio>
#include <iostream>
#include <vector>
#include <map>
#include <set>
#include <string>
#include <cstring>
#include <sstream>
#include <algorithm>
#include <functional>
#include <queue>
#include <stack>
#include <cmath>
#include <iomanip>
#include <list>
#include <bitset>
using namespace std;
inline int toInt(string s) { int v; istringstream sin(s); sin >> v; return v; }
template<class T> inline string toString(T x) { ostringstream sout; sout << x; return sout.str(); }
template<class T> inline T sqr(T x) { return x*x; }
typedef pair<int, int> P;
typedef long long ll;
typedef unsigned long long ull;

#define For(i,a,b)	for(int (i) = (a);i < (b);(i)++)
#define rep(i,n)	For(i,0,n)
#define clr(a)		memset((a), 0 ,sizeof(a))
#define mclr(a)		memset((a), -1 ,sizeof(a))
#define all(a)		(a).begin(),(a).end()
#define rall(a)		(a).rbegin(), (a).rend()
#define sz(a)		(sizeof(a))
#define Fill(a,v)	fill((int*)a,(int*)(a+(sz(a)/sz(*(a)))),v)
#define fi first
#define se second
bool cheak(int x, int y, int xMax, int yMax){ return x >= 0 && y >= 0 && xMax > x && yMax > y; }
const int dx[4] = { -1, 0, 1, 0 }, dy[4] = { 0, 1, 0, -1 };
const int mod = 1000000007;
const int INF = 20000*3;

int main()
{
	int n;
	cin >> n;
	map<int,int> sx;
	map<int,int> sy;
	sx[-INF] = INF;sx[INF] = -INF;
	sy[INF] = -INF;sy[-INF] = INF;


	int l = 20 * 20 + 20 * 20;

	rep(i, n){
		int x, y;
		cin >> x >> y;

		auto xy0 = sx.lower_bound(x);
		auto xy1 = sx.upper_bound(x);
		
		auto yx0 = sy.lower_bound(y);
		auto yx1 = sy.upper_bound(x);

		int tx[4] = {xy0->fi,xy1->fi,yx0->se,yx1->se };
		int ty[4] = {xy0->se,xy1->se,yx0->fi,yx1->fi };

		bool f = false;
		rep(j, 4){
			if(pow(x-tx[j],2)+pow(y-ty[j],2) < l){
				f = true; break;
			}
		}
		if (f)continue;

		sx[x] = y;
		sy[y] = x;
	}

	cout << sx.size()-2 << endl;

	return 0;
}