import java.util.Scanner;

/**
 * Created by sidharth on 19/9/15.
 */
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 a = sc.nextDouble();
        double b = sc.nextDouble();

        double xDist = (a - x) * (a - x);
        double yDist = (b - y) * (b - y);
        //System.out.println((xDist + yDist));
        double distance = Math.sqrt(xDist + yDist);

        int count = 0;
        while (distance > 2*r){

            distance = distance - 2 * r;
            count++;

        }if(distance != 0){

            count++;
        }


        System.out.println(count);
    }
}