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

public class Solution {
    public static void main(String[] args) { new Solution().run(); }

    private void run() {
        Scanner in = new Scanner(System.in);
        PrintWriter out = new PrintWriter(System.out);

        double r, x1, y1, x2, y2;
        r = in.nextDouble();
        x1 = in.nextDouble();
        y1 = in.nextDouble();
        x2 = in.nextDouble();
        y2 = in.nextDouble();

        double d = Math.sqrt(Math.pow(x1-x2, 2) + Math.pow(y1-y2, 2));
        out.print((long) Math.ceil(d/(r + r)));

        in.close();
        out.close();
    }
}
