#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <string>
#include <ctime>
 
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define FFOR(i,a,b) for(int i=(a);i<=(b);i++)
#define REP(i,b) FOR(i,0,b)
#define RREP(i,b) FFOR(i,1,b)
#define PB push_back
#define F first
#define S second
#define BE(c) c.begin(),c.end()
using namespace std;
typedef long long LL;
typedef LL ut;
typedef long double ld;
typedef pair<ut,ut> pr;
typedef vector<pr> Vpr;
typedef vector<ut> VI;
typedef pair<ut,pr> ppr;
typedef priority_queue<pr,Vpr, greater<pr> > PQ;
const int SIZE=1e+5 + 1;
const ut INF=1<<29;
const ld eps=1e-6;
const LL mod=1e+6 + 3;

double DP[10100];

int main() {
	int H, A, D;
	cin >> H >> A >> D;
	DP[0] = 0.0;
	FOR(i,1,H+1){
		DP[i] = min(DP[max(0, i - A)] + 1.0, DP[max(i - D, 0)] + 1.5);
	}
	cout << fixed << DP[H] << endl;
 	return 0;
}