import java.util.Scanner;


public class Main_yukicoder23 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int h = sc.nextInt();
        int a = sc.nextInt();
        int d = sc.nextInt();

        double[] e = new double[h + 1];
        e[0] = 0;

        for (int i = 1; i <= h; i++) {
        	e[i] = Math.min(1 + e[Math.max(0, i - a)], (double)3 / 2 + e[Math.max(0, i - d)]);
        }

        System.out.printf("%.3f\n", e[h]);

        sc.close();
    }
}