import java.util.Scanner;

public class cp2 {
    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 xn = sc.nextInt();
        int yn = sc.nextInt();

        double dis = Math.sqrt(((xn-x)*((xn-x)))+((yn-y)*(yn-y)));
        if(dis==0) System.out.println(0);

        else if(dis<=2*r) {
            System.out.println(1);
        }
        else{
            int op = 2*r;
            System.out.println((int)Math.ceil(dis/op));
        }
    }
}
