import java.util.*;

public class AmrAndPins {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int r = in.nextInt();
		int xi = in.nextInt();
		int yi = in.nextInt();
		int xf = in.nextInt();
		int yf = in.nextInt();
		
		double distance = Math.sqrt((yf - yi) * (yf - yi) + (xf - xi) * (xf - xi));
		System.out.println((int) Math.ceil(distance / (2 * r)));
	}
}