import java.util.*;

public class B507 {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		int r = scan.nextInt(), x = scan.nextInt(), y = scan.nextInt(), x1 = scan.nextInt(), y1 = scan.nextInt();

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

		double res = d;
		res = res / r;

		if (d == 0)
			System.out.println(0);
		else
			System.out.println((int) Math.ceil(res) - 1);
	}
}
