#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<int, ll> i_ll;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int u, v; ll w; };

ll MOD = 1000000007;
ll _MOD = 1000000009;
double EPS = 1e-10;

int main() {
	int H, A, D; cin >> H >> A >> D;
	vector<double> dp(H + 1, DBL_MAX);
	dp[0] = 0;
	for (int h = 1; h <= H; h++) {
		int ha = max(0, h - A);
		dp[h] = min(dp[h], dp[ha] + 1);
		int hd = max(0, h - D);
		dp[h] = min(dp[h], dp[hd] + 1.5);
	}
	printf("%.10f\n", dp[H]);
}