#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define mt make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

const double E = 3.0 / 4, F = 1.0 / 4, G = 2.0 / 7, H = 5.0 / 7;
double C, D;

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

    while(cin >> C >> D) {
        double lb = 0, ub = min(C/E, D/F), ml, mu;

        auto f = [&](double x) {
            double res = x*1000, c = C - x*E, d = D - x*F;
            res += min(c / G, d / H) * 2000;
            return res;
        };

        rep(i, 1000) {
            ml = (lb + lb + ub) / 3.0;
            mu = (lb + ub + ub) / 3.0;
            double xl = f(ml);
            double xu = f(mu);
            if(xl >= xu)ub = mu;
            else lb = ml;
        }
        double ans = f(lb);
        cout << setprecision(20) << ans << endl;
    }
}