import java.util.Scanner;


public class AmrAndThePins {

    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 k = sc.nextInt();
        int z = sc.nextInt();
        
        int d = (int) Math.ceil(Math.sqrt(Math.pow(z-y, 2)+ Math.pow(k-x, 2))/(2*r));
        System.out.println(d);
    }
}
