#include <bits/stdc++.h>
#define rep(i, a) for (int i = 0; i < (a); i++)
#define rep2(i, a, b) for (int i = (a); i < (b); i++)
#define repr(i, a) for (int i = (a) - 1; i >= 0; i--)
#define repr2(i, a, b) for (int i = (b) - 1; i >= (a); i--)
using namespace std;
typedef long long ll;
const ll inf = 1e9;
const ll mod = 1e9 + 7;

double dp[101010];
int H, A, D;

double rec(int H) {
	if (H <= 0) return 0;
	if (dp[H] >= 0) return dp[H];
	return dp[H] = min(1 + rec(H - A), 1.5 + rec(H - D));
}

int main() {
	cin >> H >> A >> D;

	memset(dp, -1, sizeof(dp));
	printf("%.20f\n", rec(H));	

	return 0;
}