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

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    ll A, B;
    cin >> A >> B;
    auto f = [&](double v){
        double C = A, D = B;
        C -= 3 * v / 4;
        D -= v / 4;
        if(C < 0 || D < 0) return -10000000000.0;
        double ans = 1000 * v;
        double d = min(7 * C / 2, 7 * D / 5);
        ans += 2000 * d;
        return ans;
    };
    double l = 0, r = 100000, c1, c2, v1, v2;
    for(int i = 0; i < 128; i++){
        c1 = (l * 2 + r) / 3;
        c2 = (l + 2 * r) / 3;
        v1 = f(c1), v2 = f(c2);
        if(v1 >= v2) r = c2;
        else l = c1;
    }

    cout << fixed << setprecision(15) << f(l) << '\n';
}