import java.util.Scanner;


public class Main_Round287Div2_B {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		long r = sc.nextLong();
		long x = sc.nextLong();
		long y = sc.nextLong();
		long x1 = sc.nextLong();
		long y1 = sc.nextLong();

		long dis = (x1 - x) * (x1 - x) + (y1 - y) * (y1 - y);
		long r2 = 4 * r * r;
		int ret = (int)Math.sqrt((double)dis / r2);
		if (dis % r2 != 0) {
			ret++;
		}
			
		System.out.println(ret);

		sc.close();
	}
}
