import java.util.Scanner;


public class B {
	B(){
		Scanner in = new Scanner(System.in);
		long r = in.nextLong();
		long x = in.nextLong();
		long y = in.nextLong();
		long xp = in.nextLong();
		long yp = in.nextLong();
		long d2 = (x-xp)*(x-xp) + (y-yp)*(y-yp);
		long ans = (long)Math.ceil(Math.sqrt(d2)/(2*r));
		System.out.println(ans);
	}
	public static void main(String[] args) {
		new B();
	}
}
