#include <bits/stdc++.h>

using namespace std;

const int INF = 1 << 30;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int H, A, D;
  cin >> H >> A >> D;
  vector<double> dp(H + 1, INF);
  dp[0] = 0;
  for (int i = 1; i < H + 1; i++) {
    dp[i] = min((i - A < 0 ? 0 : dp[i - A]) + 1.0,
                (i - D < 0 ? 0 : dp[i - D]) + 1.5);
  }
  cout << fixed << setprecision(10) << dp[H] << '\n';
  return 0;
}