#include<stdio.h>
#define min(a,b) a<b?a:b

int n;

double m,t,tmp,a[1001];

int main()
{
	freopen("carz.in","r",stdin);
	freopen("carz.out","w",stdout);
	int i,j;
	scanf("%d%lf",&n,&m);
	n/=10;
	m/=60;
	a[0]=-m;
	for(i=1;i<=n;i++)
	{
		a[i]=10000000;
		for(j=0;j<i;j++)
		{
			tmp=m+a[j];
			t=(i-j)*10;
			if(t>40)
				tmp+=t/70;
			else if(t>30)
				tmp+=t/75;
			else if(t>20)
				tmp+=t/80;
			else if(t>10)
				tmp+=t/90;
			else
				tmp+=t/100;
			a[i]=min(a[i],tmp);
		}
	}
	printf("%.2lf\n",a[n]);
	return 0;
}