import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		long r2 = 2 * in.nextInt();
		long x = in.nextInt();
		long y = in.nextInt();
		long x1 = in.nextInt();
		long y1 = in.nextInt();
		double R = Math.sqrt((x-x1)*(x-x1)+(y-y1)*(y-y1));

		long times = (long) R/r2;
		if (times * r2 == R) {
			System.out.println(times);
		} else {
			System.out.println(times + 1);
		}
	}

}