#include<fstream>
#include<iomanip>
using namespace std;
ifstream fin("carz.in");
ofstream fout("carz.out");
float f[102][1002],fare;//费用
int S,Sdt;
float rule[1002],T;
void init()
{
int i;
	fin>>S>>T;	
	Sdt=S/10;
	T/=60;
	rule[1]=0.1;
	rule[2]=0.2222222;
	rule[3]=0.375;
	rule[4]=0.5333333;
	for(i=5;i<=1000;i++)
		rule[i]=double(i)/7;
	for(i=1;i<=Sdt;i++)
		f[1][i]=rule[i];
}

void dp()
{
int i,j;
	for(i=2;i<=Sdt;i++)
		for(j=i;j<=Sdt;j++)
		{
			fare =T+ rule[i-1]+f[1][j-i+1];
			if(fare>f[i-1][j])
				f[i][j]=f[i-1][j];
			else
				f[i][j]=fare;
		}
	
}

int main()
{
	init();
	
	dp();
	
	fout<<setiosflags(ios::fixed)<<setprecision(2)<<f[Sdt][Sdt]<<endl;
	
	fin.close();
	fout.close();
	return 0;
}