import java.util.Scanner;


public class Main {

	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		int r=scan.nextInt();
		int x1=scan.nextInt();
		int y1=scan.nextInt();
		int x2=scan.nextInt();
		int y2=scan.nextInt();
		if(x1==x2&&y1==y2)
            System.out.println(0);
		else{
        long x=(x1-x2)*(x1-x2);
        long y=(y1-y2)*(y1-y2);
        int i=1;
        while((double)(x+y)/(i*i*4*r*r)>1)
            i++;
        System.out.println(i);
		}
	}

}

  	  				 	  	 				 			 	 	  		