
import java.awt.Point;
import java.util.Scanner;


public class Main {
   
    public static void main(String [] args){
        Scanner sc=new Scanner(System.in);
        int r=sc.nextInt();
        long x1,y1,x2,y2;
        x1=sc.nextInt();
         y1=sc.nextInt();
          x2=sc.nextInt();
          y2=sc.nextInt();
        long diff=((x1-x2)*(x1-x2))+((y1-y2)*(y1-y2));
        double res= Math.ceil(Math.sqrt(diff));
        
        System.out.println((long)Math.ceil(res/(2*r)));
    }
}
