#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <iomanip>

using namespace std;
using ll = long long;

const int INF = 100100100;

int main(){
    //cout << fixed << setpresicion(2) << endl;
    int h , a , d;
    cin >> h >> a >> d;
    vector<int> dp(h + 10100 , INF);
    dp[0] = 0;
    for(int i = 0; i <= h; i++){
        dp[i + a] = min(dp[i] + 10 , dp[i + a]);
        dp[i + d] = min(dp[i] + 15 , dp[i + d]);
    }
    int ans = INF;
    for(int i = h; i < dp.size(); i++){
        ans = min(ans , dp[i]);
    }
    //cout << ans << endl;
    string anss = to_string(ans);
    for(int i = 0; i < anss.size(); i++){
        if(i == anss.size() - 1)cout << ".";
        cout << anss[i];
    }
    cout << endl;
    return 0;
}