#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>
#include <fstream>
#include <queue>
#include <complex>

#define INF 100000000
#define INF_INT_MAX 2147483647
#define INF_LL_MAX 9223372036854775807
#define EPS 1e-10
#define Pi acos(-1)
#define LL long long
#define ULL unsigned long long

using namespace std;

int H, A, D;

int main(){

	cin >> H >> A >> D;
	double ans = INF;
	for (int a = 0; a < H / A + 2; a++){
		if (H - a*A > 0)
			ans = min(ans, (double)(a + ((H - a*A) / D + 1) * 1.5));
		else
			ans = min(ans, (double)a);
	}

	cout << ans << endl;

	return 0;

}