import java.util.Scanner;

public class AmrAndPins {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int r = sc.nextInt();
		int x = sc.nextInt();
		int y = sc.nextInt();
		int p = sc.nextInt();
		int q = sc.nextInt();
		double dis = Math.sqrt((x-p)*(x-p) + (y-q)*(y-q));
		System.out.println((int)Math.ceil(dis/(2*r)));
	}
}
