#include<iostream>
#include<vector>
#include<algorithm>
#include<functional>
#include<set>
#include<map>

int main()
{
	int H, A, D;
	std::cin >> H >> A >> D;
	std::vector<double> dp(H + 1, 100000);
	dp[0] = 0;
	for (int i = 0; i < H; ++i)
	{
		for (int k = 1; i + k <= H && k <= A; ++k)
		{
			dp[i + k] = std::min(dp[i + k], dp[i] + 1);
		}
		for (int k = 1; i + k <= H && k <= D; ++k)
		{
			dp[i + k] = std::min(dp[i + k], dp[i] + 1.5);
		}
	}
	std::cout << dp[H] << std::endl;
}