#include<iostream>
#include<cstdio>
#include<cmath>
#include<queue>
#include<vector>
#include<iomanip>
#include<algorithm>
#include<cstring>
using namespace std;
double m,t,Q,a[1001],i,j;
int main()
{
    freopen("carz.in","r",stdin);
	freopen("carz.out","w",stdout);
	int i,j,n;
	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++)
		{
			Q=m+a[j];
			t=(i-j)*10;
			if(t>40)
				Q+=t/70;
			else if(t>30)
				Q+=t/75;
			else if(t>20)
				Q+=t/80;
			else if(t>10)
				Q+=t/90;
			else
				Q+=t/100;
			a[i]=min(a[i],Q);
		}
	}
	printf("%.2lf\n",a[n]);
	return 0;
}