#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

int main()
{
    int h, a, d;
    cin >> h >> a >> d;

    vector<double> dp(h+1, 0.0);
    for(int i=1; i<=h; ++i){
        int h1 = max(0, i - a);
        int h2 = max(0, i - d);
        dp[i] = min(dp[h1] + 1, dp[h2] + 1.5);
    }
    printf("%.10f\n", dp[h]);

    return 0;
}