#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int (i) = 0 ; (i) < (int)(n) ; (i)++)
#define REP(i,a,b) for(int (i) = a ; (int)(i) <= (int)(b) ; (i)++)
#define all(n) (n).begin(),(n).end()
typedef vector<int> Vi;
typedef vector<Vi> VVi;
typedef pair<int,int> Pii;
typedef vector<Pii> VPii;

int A,D;

double dp[100010];
double dfs(int H){
	if( H <= 0 ) return 0;
	if( dp[H] != 0 ) return dp[H];
	double ans = min( dfs(H-A) + 1. ,  (dfs(H-D) * 2 / 3 + 1.) / (2./3) );
	return dp[H] = ans;
}
int main(){
	int H;
	cin >> H >> A >> D;
	printf("%.10lf\n",dfs(H));
	
}