import java.util.Scanner;
import java.io.PrintWriter;

public class p507B{
	public static void main(String []args)
	{
		Scanner in = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
			int r = in.nextInt(), x1= in.nextInt(), y1 = in.nextInt(), x2 = in.nextInt(),y2=in.nextInt();
			int res = (int)Math.ceil(Math.sqrt(Math.pow(x1-x2,2.0)+Math.pow(y1-y2,2.0))/(2*r));
			out.println(res);
		out.flush(); 
	}
}