import java.util.HashMap;
import java.util.Scanner;
 
public class cp2 {
    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 xn = sc.nextLong();
        long yn = sc.nextLong();
 
        double dis = Math.sqrt(((xn-x)*((xn-x)))+((yn-y)*(yn-y)));
        //System.out.println(dis);
        if(dis==0){
            //System.out.println("h");
            System.out.println(0);
        }
 
        else if(dis<=2*r) {
            System.out.println(1);
        }
        else{
            long op = 2*r;
            System.out.println((int)Math.ceil(dis/op));
        }
    }
}