#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

struct ExtendedSieve{
    vector<int> table;
    const int n;

    ExtendedSieve(int n) : n(n) {
        table.assign(n + 1, 0);
        table[0] = table[1] = 1;
        for(int i = 2; i <= n; ++i){
            if(table[i] > 0)    continue;
            table[i] = i;
            for(int j = i + i; j <= n; j += i){
                if(table[j] == 0)   table[j] = i;
            }
        }
    }

    int operator[](const int& k){
        return table[k];
    }

    bool is_prime(int x){
        if(x < 2)   return false;
        return x == table[x];
    }

    map<int, int> prime_factorization(int x){
        map<int, int> res;
        while(x > 1){
            ++res[table[x]];
            x /= table[x];
        }
        return res;
    }
};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int H, A, D;
    cin >> H >> A >> D;
    vector<double> dp(H + 1, -1);
    auto func = [&](auto&& self, int h) -> double {
        if(dp[h] != -1) return dp[h];
        if(h == 0)  return dp[h] = 0;
        double res = self(self, max(0, h - A)) + 1;
        chmin(res, self(self, max(0, h - D)) + 1.5);
        return dp[h] = res;
    };
    cout << fixed << setprecision(10);
    cout << func(func, H) << endl;

    return 0;
}