#ifdef __GNUC__
#pragma GCC optimize ("O3")
#pragma GCC target ("avx")
#endif

#define _USE_MATH_DEFINES

#include <iostream>
#include <iomanip>
#include <stdio.h>

#include <sstream>
#include <algorithm>
#include <cmath>

#include <string>
#include <cstring>
#include <vector>
#include <valarray>
#include <array>

#include <queue>
#include <complex>
#include <set>
#include <map>
#include <stack>
#include <list>

#include <cassert>//assert();
#include <fstream>
/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)

/////////
typedef long long LL;
typedef long double LD;
typedef unsigned long long ULL;
#define PII pair<int,int>
/////////
using namespace::std;

// 最大公約数
template<class T>
inline T gcd(T a, T b){return b == 0 ? a : gcd(b, a % b);}
// 最小公倍数
template<class T>
inline T lcm(T a, T b){return a * b / gcd(a, b);}
////////////////////////////////
pair<double,double> A,B;
double C,D;
double kakaku(double Anum){
	double Cama,Dama;
	Cama = C - A.first*Anum;
	Dama = D - A.second*Anum;
	if( Cama < 0 || Dama < 0 ){
		return 0;
	}
	double Bnum = min(Cama/B.first,Dama/B.second);
	return Anum+2*Bnum;
}

inline void solve(){
	
	cin >> C >> D;
	C *= 28000;
	D *= 28000;
	
	A.first = 21;
	A.second = 7;
	B.first = 8;
	B.second = 20;
	double Left,midL,midR,Right;
	Left = 0;
	Right = min(C/A.first,D/A.second);
	int Loop = 10000;
	while(Loop--){
		midL = (Left*2+Right)/3;
		midR = (Left+2*Right)/3;
		if( kakaku(midL)>kakaku(midR) ){
			Right = midR;
		}else{
			Left = midL;
		}
	}
	cout << kakaku((Left+Right)/2) << endl;
}

signed main(void){
	std::cin.tie(0);
	std::ios::sync_with_stdio(false);
	std::cout << std::fixed;//小数を10進数表示
	cout << setprecision(16);//小数をいっぱい表示する。16?

	solve();
}