import java.util.Scanner;

public class AmrAndPins {

    public static void main(String... args) {
        Scanner sc = new Scanner(System.in);
        long d = 2*sc.nextInt();

        long xs = sc.nextInt();
        long ys = sc.nextInt();

        long xf = sc.nextInt();
        long yf = sc.nextInt();

        long dx = xf - xs;
        long dy = yf - ys;
        long dist2 = dx * dx + dy * dy;

        long cnt = 0;
        while (cnt * cnt * d * d < dist2)
            cnt++;

        System.out.println(cnt);
    }

}
