import java.util.Scanner;

/**
 * Created by zephyr on 2/20/15.
 */
public class AmrPins {

    public static void main(String args[]) {
        Scanner cin = new Scanner(System.in);
          int r = cin.nextInt(), x = cin.nextInt(), y = cin.nextInt(), x1 = cin.nextInt(), y1 = cin.nextInt();
        double total = Math.sqrt(Math.pow(x-x1*1.0,2) + Math.pow(y - y1 * 1.0, 2));
        if (total == 0){
            System.out.println(0);
            return;
        }
        if (total <= 2 * r){
            System.out.println(1);
            return;
        }
        System.out.println((int)Math.ceil(total * 1.0 / (2 * r)));
    }

}