import java.util.Scanner;


public class B {

    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 x1 = sc.nextInt();
        int y1 = sc.nextInt();
        double d = Math.sqrt((x1 - x)*(x1 - x) + (y1 - y)*(y1 - y));
        r *= 2;
        int d1 = (int)d;
        int k = d1 / r;
        double c = d - k*r;
        System.out.println(k + (c > 0 ? 1 : 0));
    }

    
}
