#include <bits/stdc++.h>
using namespace std;

int main() {
    double C, D;
    cin >> C >> D;
    auto f = [&](double x) {
        double CC = C - x * 3.0 / 4.0;
        double DD = D - x * 1.0 / 4.0;
        double y = min(CC * 7.0 / 2.0, DD * 7.0 / 5.0);
        return 1000 * x + 2000 * y;
    };
    double low = 0;
    double high = min(4.0 / 3.0 * C, 4.0 * D);
    for (int i = 0; i < 200; i++) {
        double mid1 = (low * 2 + high) / 3;
        double mid2 = (low + high * 2) / 3;
        if (f(mid1) < f(mid2)) {
            low = mid1;
        } else {
            high = mid2;
        }
    }
    printf("%.20f\n", f(low));
}