#include "bits/stdc++.h"
using namespace std;

double dp[20000];

int main() {
	int H, A, D;
	cin >> H >> A >> D;
	for (int i = 1; i <= H; i++)
	{
		dp[i] = min(dp[max(0, i - A)] + 1, dp[max(0, i - D)] + 1.5);
	}
	printf("%.1f\n", dp[H]);
}