import java.util.Scanner;

public class b507 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int radius = sc.nextInt();
		int x = sc.nextInt();
		int y= sc.nextInt();
		int x2= sc.nextInt();
		int y2= sc.nextInt();
			
		double distance = Math.sqrt(Math.pow(x2-x, 2) + Math.pow(y2-y, 2));
		
		int steps = (int )Math.ceil(distance/(2*radius));
		System.out.println(steps);
	}
}
