#include<cstdio>
using namespace std;
const int ls[6]={0,100,90,80,75,70};
double f[1002][1002]={0};
double mn(double a,double b,double c)
{
	if(a>b)
		return a>c ? a:c;
	else
		return b>c ? b:c;
}
int s,t;
int main()
{
	freopen("carz.in","r",stdin);
	freopen("carz.out","w",stdout);
	int s,t,i,j,k;
	scanf("%d%d",&s,&t);
	for(i=s/10;i>=0;i--)
	{
		for(j=i+1;j<=s/10;j++)
		{
			for(k=i;k<=j;k++)
			{
				if(j-i<1)
					break;
				f[i][j]=mn(f[i][k]+f[k][j],10*double(j-i)/ls[(j-i)%6]+t/60,f[i][j]);
			}
		}
	}
	printf("%.2lf",f[0][s/10]);
	return (0);
}