#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>
#include <string>

using namespace std;

const int XY_MAX = 20000;
const int R = 10;
const int LEN = 2 * R;
const int LEN2 = LEN * LEN;

vector< vector<bool> > board;

bool possible(int x, int y) {
	int dx, dy, nx, ny;
	for (dx = -LEN; dx <= LEN; dx++) {
		nx = x + dx;
		if (nx < 0 || XY_MAX < nx) {
			continue;
		}

		for (dy = -LEN; dy <= LEN; dy++) {
			ny = y + dy;
			if (ny < 0 || XY_MAX < ny) {
				continue;
			}

			if (dx * dx + dy * dy >= LEN2) {
				continue;
			}

			if (board[ny][nx]) {
				return false;
			}
		}
	}
	return true;
}

int main() {
	int n, x, y;
	board.assign(XY_MAX + 1, vector<bool>(XY_MAX + 1, false));

	cin >> n;
	int coin = 0;
	for (int i = 0; i < n; i++) {
		cin >> x >> y;

		if (possible(x, y)) {
			coin++;
			board[y][x] = true;
		}
	}

	cout << coin << endl;
	return 0;
}