import java.io.*;
import java.util.*;

public class b1 {
	public static void main(String[] args) throws FileNotFoundException {
		Scanner in = new Scanner(System.in);
		PrintWriter out = new PrintWriter(System.out);
		
		int r = in.nextInt();
		int x0 = in.nextInt();
		int y0 = in.nextInt();
		
		int x1 = in.nextInt();
		int y1 = in.nextInt();
		
		double dist = Math.sqrt((1l * (x0 - x1) * (x0 - x1) + 1l * (y0 - y1) * (y0 - y1)));
		
		int ans = 0;
		while (dist - 2 * r > 0){
			dist -= 2 * r;
			ans++;
		}
		
		if (dist != 0){
			ans += 1;
		}
		
		out.println(ans);
		out.close();
	}
}
