import java.util.Scanner;

public class amrPins {

	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 x1=sc.nextInt();
		int y1=sc.nextInt();
		int a=Math.abs(x1-x);
		int b=Math.abs(y1-y);
		double d=Math.sqrt(Math.pow(a, 2)+Math.pow(b, 2));
		int ans=(int)Math.ceil(d/(2*r));
		System.out.println(ans);
	}
}
