import java.util.Arrays;
import java.util.Scanner;

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

	void run() {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		double a = sc.nextDouble();
		double b = sc.nextDouble();
		double r = 1 / (4 * a) - 1 / (4 * b);
		double h = (n - 1) * r;
		double m = 1 / (4 * a) + 1 / (4 * b);
		double r2 = 0.5 * (1 / (Math.sqrt(h * h + m * m) - r) - 1 / (Math.sqrt(h * h + m * m) + r));
		System.out.println(String.format("%.20f", r2));
	}

	void tr(Object... objects) {
		System.out.println(Arrays.deepToString(objects));
	}

}