import java.util.Scanner;
import java.io.PrintWriter;
import java.util.Arrays;

public class Smile {
	static Scanner in;
	static PrintWriter out;	

	public static void main(String[] args) {
		in = new Scanner(System.in);
		out = new PrintWriter(System.out);
		int r = in.nextInt();
		int x1 = in.nextInt();
		int y1 = in.nextInt();
		int x2 = in.nextInt();
		int y2 = in.nextInt();
		double l = Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
		double ans = l / (2 * r);
		int dx = (int) ans;
//		out.println(dx + " " + ans);
		if (dx < ans) {
			out.println(dx + 1);
		} else {
			out.println(dx);
		}
		
//		out.println(ans);
		
		out.close();
}
}