#include <iostream>
#include <cstdio>

using namespace std;

typedef long double LD;

const LD EPS = 1e-9L;

LD c, d, l, r, m1, m2, c1, d1;

LD Calc(LD v) {
    LD ret = 4000.0L * v;
    LD c2 = c - v * 3, d2 = d - v;
    LD x = min(7 * c2 / 2, 7 * d2 / 5);
    ret += 2000.0L * x;
    return ret;
}

int main() {
    scanf("%Lf%Lf", &c, &d);

    l = 0.0L, r = min(c / 3, d);
    while (r - l > EPS) {
        m1 = l + (r - l) / 3;
        m2 = l + (r - l) / 3 * 2;
        if (Calc(m1) < Calc(m2)) {
            l = m1;
        } else {
            r = m2;
        }
    }
    printf("%.9Lf\n", Calc(l));

    return 0;
}