import java.util.Scanner;

public class B287 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int r = sc.nextInt();
        long x = sc.nextInt();
        long y = sc.nextInt();
        long x2 = sc.nextInt();
        long y2 = sc.nextInt();

        double dist = Math.sqrt((x2 - x) * (x2 - x) + (y2 - y) * (y2 - y));
        System.out.println((int)Math.ceil(dist/(r * 2)));

    }
}
