import java.util.Scanner;
public class Main{
	public static void main(String args[]){
		Scanner sc=new Scanner(System.in);
		double r=sc.nextDouble();
		double x=sc.nextDouble();
		double y=sc.nextDouble();
		double x1=sc.nextDouble();
		double y1=sc.nextDouble();
		double dist=Math.sqrt((x1-x)*(x1-x)+(y1-y)*(y1-y));
		System.out.println((int)Math.ceil(dist/2/r));
	}
}