import java.util.Scanner;

/**
 * Created by Saksham on 9/19/2015.
 * 507B
 */
public class AmrAndPins {
    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 count = 0;
        double dist = Math.sqrt(((x1 - x) * (x1 - x)) + ((y1 - y) * (y1 - y)));
        while (dist > 2 * r) {
            dist = dist - (2 * r);
            count++;
        }
        if (dist != 0) {
            count++;    //last move needed when dist<=2r to coincide the centers
        }
        System.out.println(count);
    }
}
