import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int h = sc.nextInt();
        int a = sc.nextInt();
        int d = sc.nextInt();
        TreeMap<Double, Integer> status = new TreeMap<>();
        status.put(0.0, h);
        double ans = Double.MAX_VALUE;
        while (status.size() > 0) {
            Map.Entry<Double, Integer> entry = status.pollFirstEntry();
            if (entry.getValue() <= a) {
                ans = Math.min(entry.getKey() + 1, ans);
            } else {
                double nextKey = entry.getKey() + 1;
                int nextValue = entry.getValue() - a;
                if (!status.containsKey(nextKey) || status.get(nextKey) > nextValue) {
                    status.put(nextKey, nextValue);
                }
            }
            if (entry.getValue() <= d) {
                ans = Math.min(entry.getKey() + 1.5, ans);
            } else {
                double nextKey = entry.getKey() + 1.5;
                int nextValue = entry.getValue() - d;
                if (!status.containsKey(nextKey) || status.get(nextKey) > nextValue) {
                    status.put(nextKey, nextValue);
                }
            }
        }
        System.out.println(ans);
    }
}