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

int main(void) {
	int H, A, D;
	cin >> H >> A >> D;
	
	vector<double> dp(H + 1, 1e9);
	auto solve = [&](auto &&solve, int v) ->double {
		if(v <= 0) return 0;
		if(dp[v] != 1e9) return dp[v];
		return dp[v] = min(solve(solve, v - A) + 1, solve(solve, v - D) + 3.0 / 2);
	};
	
	cout << solve(solve, H) << endl;
	return 0;
}