import java.util.Scanner;


public class AmrPins {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in = new Scanner(System.in);
        int r = in.nextInt();
        int x1 = in.nextInt();
        int y1 = in.nextInt();
        int x2 = in.nextInt();
        int y2 = in.nextInt();
        
        int dx = Math.abs(x1 - x2);
        int dy = Math.abs(y1 - y2);
        double dist = Math.sqrt(dx * dx + dy * dy);
        
        
//      int res = (int) (Math.floor(dist) / (2 * r));
        int res = 0;
        double d = 0;
        while (d < dist) {
            res++;
            d += 2 * r;
        }
        
        System.out.println(res);
    }

}
