import java.util.*;
public class circle{
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		long r=sc.nextLong();
		long x=sc.nextLong();
		long y=sc.nextLong();
		long x1=sc.nextLong();
		long y1=sc.nextLong();
		double d=Math.sqrt(((x1-x)*(x1-x))+((y1-y)*(y1-y)));
		//System.out.println(d);
		long move=(long)Math.ceil(d/(2*r));
		System.out.println(move);



	}
}