using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class TEST{
	static void Main(){
		Sol mySol =new Sol();
		mySol.Solve();
	}
}

class Sol{
	public void Solve(){
		
		double l = 0;
		double r = C;
		
		Func<double,double> f = x =>{
			double ca = x;
			double da = x/3.0;
			if(da > D){
				da = D;
				ca = 3.0*da;
			}
			
			double drest = D - da;
			double cb = C - ca;
			double db = cb /2.0*5.0;
			if(db > drest){
				db = drest;
				cb = db /5.0 * 2.0;
			}
			return 1000*(ca+da)+2000*(cb+db);
		};
		
		for(int t=200;t>=0;t--){
			
			if(f((2*l + r)/3) > f((l+2*r)/3)){
				r = (l+2*r)/3;
			}else{
				l = (2*l+r)/3;
			}
		}
		
		double ret = f((l+r)/2);
		
		Console.WriteLine(ret);
	}
	double C,D;
	public Sol(){
		var d = rda();
		C = d[0]; D = d[1];
	}

	static String rs(){return Console.ReadLine();}
	static int ri(){return int.Parse(Console.ReadLine());}
	static long rl(){return long.Parse(Console.ReadLine());}
	static double rd(){return double.Parse(Console.ReadLine());}
	static String[] rsa(char sep=' '){return Console.ReadLine().Split(sep);}
	static int[] ria(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>int.Parse(e));}
	static long[] rla(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>long.Parse(e));}
	static double[] rda(char sep=' '){return Array.ConvertAll(Console.ReadLine().Split(sep),e=>double.Parse(e));}
}