import java.util.*;
public class Car {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int r = sc.nextInt();
		int x1 = sc.nextInt();
		int y1 = sc.nextInt();
		int x2 = sc.nextInt();
		int y2 = sc.nextInt();
		int moves = (int)Math.ceil(Math.sqrt(Math.pow(x2 - x1, 2) + Math.pow(y2 - y1, 2)) / (2 * r));
		System.out.print(moves);
	}
}