import java.util.Scanner;


public class CFB {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		double r = in.nextDouble();
		double x = in.nextDouble();
		double y = in.nextDouble();
		double x1 = in.nextDouble();
		double y1 = in.nextDouble();
		double d = Math.sqrt((x-x1)*(x-x1)+(y-y1)*(y-y1));
		System.out.println((int) Math.ceil(d/(r*2)));
	}

}
