import java.util.*;

public class Ciircu {

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String[] rxyuv = sc.nextLine().split(" ");
		int r = Integer.valueOf(rxyuv[0]);
		int x = Integer.valueOf(rxyuv[1]);
		int y = Integer.valueOf(rxyuv[2]);
		int u = Integer.valueOf(rxyuv[3]);
		int v = Integer.valueOf(rxyuv[4]);

		double d = (u - x) * (u - x) + (v - y) * (v - y);
		d = Math.sqrt(d);
		d = Math.ceil(d);
		d = Math.ceil(d /( 2*r));
		System.out.println((int) d);

	}

}
