#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <iomanip>

#define REP(i, a, b) for (int i = int(a); i < int(b); i++)
#define dump(val) cerr << __LINE__ << ":\t" << #val << " = " << (val) << endl

using namespace std;

typedef long long int lli;

template<typename T>
vector<T> make_v(size_t a, T b) {
    return vector<T>(a, b);
}

template<typename... Ts>
auto make_v(size_t a, Ts... ts) {
    return vector<decltype(make_v(ts...))>(a, make_v(ts...));
}

int main() {
    int H, A, D;
    cin >> H >> A >> D;
    double ans = 1e+9;
    REP(i, 0, (H + A - 1) / A + 1) {
        int rem = max(H - i * A, 0);
        ans = min(ans, i + 1.5 * ((rem + D - 1) / D));
    }
    cout << fixed << setprecision(10) << ans << endl;
    return 0;
}