import java.util.Scanner;

public class amrANDpinsCodf {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner s = new Scanner(System.in);
		long r = s.nextInt();
		long x = s.nextInt();
		long y = s.nextInt();
		long x1 = s.nextInt();
		long y1 = s.nextInt();
		double d = (double) Math.sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
		long n = 2 * r;
		System.out.println((int)Math.ceil(d/n));
	}

}
