#include <iostream>
using namespace std;

const int kMAX_H = 10010;

int H, A, D;
double memo[kMAX_H];

double E(int x) {
    if (memo[x] >= 0) return memo[x];
    if (x >= H) return memo[x] = 0.0;
    double res;
    res = min(E(x + A) + 1.0, E(x + D) + 3.0 / 2.0);

    return memo[x] = res;
}

void Solve() {
    fill(memo, memo + kMAX_H, -1.0);
    cout << E(0) << endl;
}

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

    Solve();

    return 0;
}