#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)

#define MP make_pair
#define MT make_tuple
#define EACH(i,c) for(auto i: c)
#define SORT(c) sort((c).begin(),(c).end())

#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()

#define E (0.0000000001)

int main() {
	int C, D;
	cin >> C >> D;
	double left, right;
	left = 0;
	right = min(C / (3 / 4.0), D / (1 / 4.0));

	auto f = [&](double A){
		double B;
		B = min((C - A * (3 / 4.0)) / (2 / 7.0), (D - A * (1 / 4.0)) / (5 / 7.0));
		return A * 1000 + B * 2000;
	};

	while(right - left > E){
		double left_third = left + (right - left) / 3;
		double right_third = right - (right - left) / 3;
		if(f(left_third) < f(right_third)){
			left = left_third;
		}
		else{
			right = right_third;
		}
	}

	printf("%.8f\n", f((left + right) / 2));

	return 0;
}