import java.util.Scanner;


public class prob3 {
	
	public static long generer(int r,int x,int y,int x1,int y1)
	{
		long res;
	/*	
		res=( Math.abs(x-x1)-(Math.abs(x-x1)%(2*r)) )/(2*r);

		res+=( Math.abs(y-y1)-(Math.abs(y-y1)%(2*r)) )/(2*r);
		
		if(Math.abs(x-x1)%(2*r)!=0 || Math.abs(y-y1)%(2*r)!=0 )
			res++;*/
		
		double distance=(Math.pow((x-x1),2)+Math.pow((y-y1),2));
		distance=Math.sqrt(distance);
		res=(long)(distance-(distance%r))/(2*r);
		System.out.println(res);
		if(distance%(2*r)!=0)
		res++;
		
		return res;
	}
	
	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();
		
		System.out.println(generer(r,x,y,x1,y1));
	}

}
