#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const double A11 = 3.0 / 4;
const double A12 = 2.0 / 7;
const double A21 = 1.0 / 4;
const double A22 = 5.0 / 7;
double C, D;

const double eps = 1e-10;
bool In(double x1, double x2) {
	if(x1 < 0 || x2 < 0) return false;
	double c = x1 * A11 + x2 * A12;
	double d = x1 * A21 + x2 * A22;
	return 0 <= c && c <= C + eps && 0 <= d && d <= D + eps;
}

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	cin >> C >> D;

	double ans = 0;

	ans = max(ans, 1000 * min(C / A11, D / A21));
	ans = max(ans, 2000 * min(C / A12, D / A22));

	double x2 = (A21 * C - A11 * D) / (A12 * A21 - A22 * A11);
	double x1 = (C - A12 * x2) / A11;
	if(In(x1, x2)) {
		ans = max(ans, 1000 * x1 + 2000 * x2);
	}
	cout << fixed << setprecision(15) << ans << endl;
}