#include <iostream>
#include <cstdint>
#include <algorithm>
#include <iomanip>

using namespace std;

int main() {

  ios::sync_with_stdio(false);
  cin.tie(0);

  int h, a, d;
  cin >> h >> a >> d;
  double dp[10001];
  for (int i = 1; i <= h; i++) {
    dp[i] = min(dp[max(0, i - a)] + 1, dp[max(0, i - d)] + 1.5);
  }
  cout << fixed << setprecision(2) << dp[h] << endl;
  return 0;
}