#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
#ifdef __LOCAL
 #include <debug>
#else
 #define debug(...) void(0)
#endif

#define REP(i,n) for(int i=0;i<(n);i++)
#define ALL(v) v.begin(),v.end()

template<typename T>
istream& operator>>(istream&is,vector<T>&v){
  for(T&p:v)is>>p;
  return is;
}
template<typename T>
ostream& operator<<(ostream&os,const vector<T>&v){
  if(&os==&cerr)os<<"[";
  for(int i=0;i<v.size();i++){
    os<<v[i];
    if(i+1<v.size())os<<(&os==&cerr?",":" ");
  }
  if(&os==&cerr)os<<"]";
  return os;
}

using ld=long double;

int main(){
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int h,a,d;cin>>h>>a>>d;

  vector<ld> ans(h+1,-1);
  ans[0]=0;
  auto f=[&](auto f,int x)->ld{
    if(ans[x]>=0)return ans[x];
    ans[x]=f(f,max(x-a,0))+1;
    ans[x]=min(ans[x],f(f,max(x-d,0))+1.5);
    return ans[x];
  };
  cout<<fixed<<setprecision(12)<<f(f,h)<<endl;
}