#include <cstdio>
#include <cstring>
#include <iostream>
#include <string>
#include <cmath>
#include <bitset>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <algorithm>
#include <complex>
#include <unordered_map>
#include <unordered_set>
#include <random>
#include <cassert>
using namespace std;
typedef long long int ll;
typedef pair<int, int> P;

int main()
{
	double p1=0, p2=5000;
	double c, d; cin>>c>>d;
	for(int t=0; t<100; t++){
		double p=(p1+p2)/2;
		if(max(0.0, 14*(3*p/4-c)/17)<=min(p/2, 14*(d-p/4)/3)) p1=p;
		else p2=p;
	}
	printf("%.7lf\n", p1*1000);
	return 0;
}