import java.util.Scanner;

public class P2 {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int r=s.nextInt(),x1=s.nextInt(),y1=s.nextInt(),x2=s.nextInt(),y2=s.nextInt();
		System.out.println((long)Math.ceil((Math.pow((Math.pow(x2-x1, 2)+Math.pow(y2-y1, 2)), 0.5))/(2*r)));
	
	
	
	
	}
}
