#include<bits/stdc++.h>
using namespace std;

signed main(){
    int h,a,d;
    cin>>h>>a>>d;
    vector<double> dp(h+1,0);
    for(int i=1;i<=h;i++){
        dp[i]=min(1.0+dp[max(0,i-a)],1.5+dp[max(0,i-d)]);
    }
    cout<<setprecision(10)<<dp[h]<<endl;
}