import java.util.Scanner;


public class b {
	public static void main(String[] args) {
		Scanner scanner = new Scanner(System.in);
		
		long r = scanner.nextInt();
		long x = scanner.nextInt();
		long y = scanner.nextInt();
		long xp = scanner.nextInt();
		long yp = scanner.nextInt();
		
		long dx = xp - x;
		long dy = yp - y;
		long dist = dx*dx + dy*dy;
		long cdist = 4*r*r;
		
		double counts = Math.sqrt(dist / (double) cdist);
		long steps = (long) Math.ceil(counts);
		
		System.out.println(steps);
	}
}
