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

public class Main {
    
    static Scanner in = new Scanner(System.in);
    static PrintWriter out = new PrintWriter(System.out);
    
    public static void main(String[] args) {
        int r = in.nextInt(), x1 = in.nextInt(), y1 = in.nextInt(), x2 = in.nextInt(), y2 = in.nextInt(), dx = x1 - x2, dy = y1 - y2;
        out.print((int)Math.ceil(Math.sqrt(dx * dx + dy * dy) / (2.0 * r)));
        out.close();
    }
}