import java.util.Scanner;

public class AmrAndPins 
{
	public static void main(String[] args) 
	{
		Scanner sc = new Scanner(System.in);
		int r = sc.nextInt();
		int x = sc.nextInt();
		int y = sc.nextInt();
		int xp = sc.nextInt();
		int yp = sc.nextInt();
		
		double d = Math.sqrt((xp-x)*(xp-x) + (yp - y)*(yp - y));
		int n = (int)(Math.ceil(d/(2*r)));
		System.out.println(n);
	}
}
