#include <iostream>
#include <complex>
#include <list>

class Ichien {
	std::complex<double> point;
public:
	Ichien(double x, double y) : point(x, y) {
	};
	bool kasanaru(Ichien *other) {
		return std::abs(this->point - other->point) < 20;
	}
};

int main() {
	int n;
	double x, y;
	Ichien *ichi;
	std::list<Ichien *> list;

	std::cin >> n;
	for (int i = 0; i < n; ++i) {
		std::cin >> x >> y;
		ichi = new Ichien(x, y);
		bool okeru = true;
		for (auto other: list) {
			if (ichi->kasanaru(other)) {
				okeru = false;
				break;
			}
		}
		if (okeru) {
			list.push_back(ichi);
		} else {
			delete ichi;
		}
	}
	std::cout << list.size() << std::endl;
	return 0;
}