import java.util.Scanner;
public class ahmed
{
    public static void main(String args[])
	{
		Scanner scn = new Scanner(System.in);
		int r = scn.nextInt();
		int x = scn.nextInt();
		int y = scn.nextInt();
		int x1 = scn.nextInt();
		int y1 = scn.nextInt();
		int ans = 0;
		double x2 = x1 - x;
		double y2 = y1 - y;
		ans = (int)Math.ceil((double)((Math.sqrt(Math.pow(x2, 2) + Math.pow(y2, 2))) / (2 * r)));
		System.out.println(ans);
	}

}