#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream in("carz.in");
ofstream out("carz.out");
int S;
double T;
double f[4001]={0};
double V[4001]={0};
double ans=0;
double INF=9999999;
void read()
{
	int i,j;
	in>>S>>T;
	S/=10;
	T/=60;
	for(i=0;i<=4000;i++)f[i]=INF;
}
void print(double a)
{
	out<<setprecision(2)<<std::fixed<<a;
}
void work()
{
	int i,j;
	f[0]=0;
	f[1]=0.1;
	for(i=5;i<=4000;i++)V[i]=7;
	V[0]=V[1]=10;
	V[2]=9;
	V[3]=8;
	V[4]=7.5;
	for(i=2;i<=S;i++)
	{
		for(j=0;j<i;j++)
		{
			if(j!=0)f[i]=min(f[i],f[j]+((i-j)/V[i-j])+T);
			else f[i]=min(f[i],f[j]+((i-j)/V[i-j]));
		}
	}
	//for(i=0;i<=S;i++)out<<f[i]<<endl;
}
int main()
{
	read();
	work();
	print(f[S]);
	return 0;
}