#include <bits/stdc++.h>

using namespace std;

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

//container util
//------------------------------------------
#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())

//repetition
//------------------------------------------
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)

//constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI  = acos(-1.0);

int H, A, D;

int main(){
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  cin >> H >> A >> D;
  vector<double> dp(H+1, 0);
  dp[0] = 0;
  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(9) << dp[H] << endl;

  return 0;
}