import java.util.*;
public class a {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		double r = in.nextDouble() * 2.0;
		double x = in.nextDouble();
		double y = in.nextDouble();
		double x1 = in.nextDouble();
		double y1 = in.nextDouble();
		double dist = Math.sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y));
		int steps = (int)Math.ceil(dist / r);
		System.out.println(steps);
	}
}