#include <iostream>
#include <string>
#include <queue>
#include <stack>
#include <algorithm>
#include <list>
#include <vector>
#include <complex>
#include <utility>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <bitset>
#include <ctime>
#include <map>
#include <unordered_map>
#include <set>
#include <unordered_set>
#include <cassert>
#include <cstddef>
#include <iomanip>
#include <numeric>
#include <tuple>
#include <sstream>
#include <fstream>
#include <chrono>

using namespace std;
#define REP(i, n) for (int (i) = 0; (i) < (n); (i)++)
#define FOR(i, a, b) for (int (i) = (a); (i) < (b); (i)++)
#define RREP(i, a) for(int (i) = (a) - 1; (i) >= 0; (i)--)
#define FORR(i, a, b) for(int (i) = (a) - 1; (i) >= (b); (i)--)
#define DEBUG(C) cerr << #C << " = " << C << endl;
using LL = long long;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<LL>;
using VVL = vector<VL>;
using VD = vector<double>;
using VVD = vector<VD>;
using PII = pair<int, int>;
using PDD = pair<double, double>;
using PLL = pair<LL, LL>;
using VPII = vector<PII>;
template<typename T> using VT = vector<T>;
#define ALL(a) begin((a)), end((a))
#define RALL(a) rbegin((a)), rend((a))
#define SORT(a) sort(ALL((a)))
#define RSORT(a) sort(RALL((a)))
#define REVERSE(a) reverse(ALL((a)))
#define MP make_pair
#define FORE(a, b) for (auto &&a : (b))
#define FIND(s, e) ((s).find(e) != (s).end())
#define EB emplace_back
template<typename T> inline bool chmax(T &a, T b){if (a < b){a = b;return true;}return false;}
template<typename T> inline bool chmin(T &a, T b){if (a > b){a = b;return true;}return false;}

const int INF = 1e9;
const int MOD = INF + 7;
const LL LLINF = 1e18;
const long double EPS = 1e-9;

double C, D;
double calc(double useCforMakeA) {
    double res = 0.0;
    double makeA = useCforMakeA / (1. * 3 / 4);
    if (makeA / 4 > D) {
        makeA = D * 4;
        useCforMakeA = makeA * (1. * 3 / 4);
    }
    res += makeA * 1000;
    double prec = C - useCforMakeA;
    double pred = D - makeA / 4;
    res += min(prec / (1. * 2 / 7), pred / (1. * 5 / 7)) * 2000;
    return res;
}

int main(void) {
    cin >> C >> D;
    double Chigh = C, Clow = 0;
    for (int i = 0; i < 1e5; ++i) {
        const double midlow = (Chigh + Clow * 2) / 3;
        const double midhigh = (Chigh * 2 + Clow) / 3;
        if (calc(midlow) > calc(midhigh)) Chigh = midhigh;
        else Clow = midlow;
    }
    cout << fixed << setprecision(10) << calc(Clow) << endl;
}