import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		try (Scanner scanner = new Scanner(System.in)) {
			double r = scanner.nextDouble();
			double x = scanner.nextDouble();
			double y = scanner.nextDouble();
			double x1 = scanner.nextDouble();
			double y1 = scanner.nextDouble();

			double distance = Math.sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y));

			int ans = (int)(distance/(2 * r));

			if((distance%(2*r)) > 0) {
				ans += 1;
			}
			
			System.out.println(ans);
		}
	}
}
