import java.util.*;
public class CC {
	
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int r = scan.nextInt();
		int x = scan.nextInt();
		int y = scan.nextInt();
		int x2 = scan.nextInt();
		int y2 = scan.nextInt();
		System.out.println((int)Math.ceil(Math.pow(Math.pow((x-x2), 2)+Math.pow(y-y2, 2),0.5)/2/r));
	}

}
