#include<iostream>
#include<cstdio>
#include<iomanip>
using namespace std;
int s;
double sum[1001][1001]={0},f[1001][1001]={0},t;
double sudu(double x);
double minn(double y,double z,double w);
int main()
{
	freopen("carz.in","r",stdin);
	freopen("carz.out","w",stdout);
	cin>>s>>t;
	s=s/10;
	for(int i=0;i<s;i++)
	{
		sum[i][i]=0;
		for(int j=i+1;j<=s;j++)
		{
			sum[i][j]=sudu(double((j-i+1)*10));
		}
	}
	for(int l=2;l<=s;l++)
	{
		for(int i=0;i<=s-l+1;i++)
		{
			int j=i+l-1;
			f[i][j]=200000;
			for(int k=i;k<=j;k++)
			{
				f[i][j]=minn(f[i][j],f[i][k]+f[k][j]+double(t/60),sum[i][j]);
			}
		}
	}
	cout<<setiosflags(ios::fixed)<<setprecision(2)<<f[1][s]<<endl;
}
double sudu(double x)
{
	double c;
	if(x<=10)
	{
		c=double(double(x)/100);
	}
	if(x>10&&x<=20)
	{
		c=double(double(x)/90);
	}
	if(x>20&&x<=30)
	{
		c=double(double(x)/80);
	}
	if(x>30&&x<=40)
	{
		c=double(double(x)/75);
	}
	if(x>40)
	{
		c=double(double(x)/70);
	}
	return c;
}
double minn(double y,double z,double w)
{
	double l=0;
	if(y<z&&y<w)
	{
		l=y;
	}
	else
	{
		if(z<w)
		{
			l=z;
		}
		else
			l=w;
	}
	return l;
}