import java.util.Scanner;


public class AmrPins {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in = new Scanner(System.in);
        long r = in.nextInt();
        long x1 = in.nextInt();
        long y1 = in.nextInt();
        long x2 = in.nextInt();
        long y2 = in.nextInt();
        
        long dx = Math.abs(x1 - x2);
        long dy = Math.abs(y1 - y2);
        
        long distSqr = dx * dx + dy * dy;
        
        double dist = Math.sqrt(dx * dx + dy * dy);
        
        int res = (int)Math.ceil(dist / (2.0 * r));
        
//      int res = 0;
//      double d = 0;
//      while (d < dist) {
//          res++;
//          d += 2 * r;
//      }
        
        System.out.println(res);
    }

}
