import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final int H = sc.nextInt();
		final int A = sc.nextInt();
		final int D = sc.nextInt();
		
		double[] DP = new double[H + 1];
		Arrays.fill(DP, Double.MAX_VALUE);
		DP[0] = 0;
		for(int i = 1; i <= H; i++){
			DP[i] = Math.min(DP[Math.max(i - A, 0)] + 1.0, DP[Math.max(i - D, 0)] + 1.5);
		}
		
		System.out.printf("%.8f\n", DP[H]);
		
	}

}