#include <algorithm>
#include <iostream>
#include <cstdio>
#include <map>
#include <numeric>
#include <cmath>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <queue>
#include <complex>
#include <string.h>
#include <unordered_set>
#include <unordered_map>
using namespace std;

#define endl '\n'
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define uniq(v) (v).erase(unique((v).begin(), (v).end()), (v).end())

typedef long long ll;
typedef pair<int, int> P;
typedef unsigned int uint;
typedef unsigned long long ull;
struct pairhash {
public:
    template<typename T, typename U>
    size_t operator()(const pair<T, U> &x) const {
	size_t seed = hash<T>()(x.first);
	return hash<U>()(x.second) + 0x9e3779b9 + (seed<<6) + (seed>>2);
    }
};

const int inf = 1000000009;

unordered_map<int, double> memo;
int a, d;

double calc(int h) {
    if (memo.count(h) == 0) {
	if (h <= a) {
	    if (0 < h)
		memo[h] = 1;
	    else
		memo[h] = 0;
	} else {
	    double res = calc(h-a) + 1;
	    res = min(res, calc(h-d) + 1.5);
	    memo[h] = res;
	}
    }
    return memo[h];
}

int main() {
    int h;
    scanf("%d%d%d", &h, &a, &d);
    printf("%.15f\n", calc(h));
}