import java.util.Scanner;


public class AmrAndPins {
	public static void main(String[] args) {
		Scanner sc= new Scanner(System.in);
		double r= sc.nextDouble();
		double x= sc.nextDouble();
		double y= sc.nextDouble();
		double x2= sc.nextDouble();
		double y2= sc.nextDouble();
		double dist= Math.sqrt(Math.pow(y2-y, 2)+Math.pow(x2-x, 2));
		double result= Math.ceil(dist/(2*r));
		System.out.println((int)(result));
	}

}
