#include<iostream>
#include<cstdio>
#include<algorithm>
#include<iomanip>
using namespace std;
double dp[1005];
double min(double a,double b)
{
	return a<b?a:b;
}
int main()
{
	freopen("carz.in","r",stdin);
	freopen("carz.out","w",stdout);
	int s;double t;
	cin>>s>>t;
	s/=10;
	for(int i=1;i<=s;i++)
		dp[i]=0x7fffff;
	for(int i=1;i<=s;i++)
	{
		
		for(int j=0;j<i;j++)
		{
			if(i-j==1)
				dp[i]=min(dp[j]+10.0/100.0+t/60.0,dp[i]);
			if(i-j==2)
				dp[i]=min(dp[j]+20.0/90.0+t/60.0,dp[i]);
			if(i-j==3)
				dp[i]=min(dp[j]+30.0/80.0+t/60.0,dp[i]);
			if(i-j==4)
				dp[i]=min(dp[j]+40.0/75.0+t/60.0,dp[i]);
			if(i-j>4)
				dp[i]=min(dp[j]+(i-j)*10.0/70.0+t/60.0,dp[i]);
		}
	}
	cout<<setiosflags(ios::fixed)<<setprecision(2);
	cout<<dp[s]-t/60.0;
	return 0;
}