#include <iostream>
#include <cstdio>
using namespace std;

int s,t,s1;
double ans,temp;
int cnt;
int main()
{
	freopen("carz.in","r",stdin);
	freopen("carz.out","w",stdout);
	
	cin>>s>>t;
	
	//足够，不用加油 
	ans=s*1.0/70;
	
	//最多40
	cnt=s/40;
	temp=(cnt*40)/75.0+(cnt-1)*t/60.0;
	s1=s-cnt*40;
	if (s1>0 && s1<=10)
		temp+=s1/100.0+t;
	else if (s1>10 && s1<=20)
		temp+=s1/90.0+t;
	else if (s1>20 && s1<=30)
		temp+=s1/80.0+t;
	else if (s1>30 && s1<=40)
		temp+=s1/75.0+t;
	if (temp<ans) ans=temp;
	
	//最多30
	cnt=s/30; 
	temp=(cnt*30)/80.0+(cnt-1)*t/60.0;
	s1=s-cnt*30;
	if (s1>0 && s1<=10)
		temp+=s1/100.0+t;
	else if (s1>10 && s1<=20)
		temp+=s1/90.0+t;
	else if (s1>20 && s1<=30)
		temp+=s1/80.0+t;
	if (temp<ans) ans=temp;
	
	//最多20
	cnt=s/20;
	temp=(cnt*20)/90.0+(cnt-1)*t/60.0;
	
	s1=s-cnt*20;
	if (s1>0 && s1<=10)
		temp+=s1/100.0+t;
	else if (s1>10 && s1<=20)
		temp+=s1/90.0+t;
	if (temp<ans) ans=temp;
	
	//最多10
	temp=s*1.0/100+s*1.0/10*t/60;
	if (temp<ans) ans=temp;
	
	printf("%.2lf\n",ans); 
	return 0;
}