#include <bits/stdc++.h>
using namespace std;
//#include <atcoder/all>
//using namespace atcoder;
using ll=long long;
using Graph=vector<vector<int>>;
#define MAX 1000000
#define MOD 1000000009
//#define MOD 998244353
#define INF 1000000000
//#define INF 1000000000000000000

int main(){
  int H,A,D;
  cin>>H>>A>>D;
  vector<double> dp(H+1,1e10);
  dp[0]=0.0;
  for(int i=1;i<=H;i++){
    dp[i]=min(dp[max(0,i-A)]+1.0,dp[max(0,i-D)]+1.5);
  }
  printf("%.6lf\n",dp[H]);
}