import java.util.*;
public class B_Amr_and_Pins {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        StringBuilder out = new StringBuilder();
        double r,x,y,x1,y1;
        r = in.nextInt();
        x = in.nextInt();
        y = in.nextInt();
        x1 = in.nextInt();
        y1 = in.nextInt();
        double d = Math.sqrt(((x-x1)*(x-x1))+((y-y1)*(y-y1)));
        out.append((int)Math.ceil(d /(2*r))+"\n");
        System.out.print(out);
    }
    
}
