#include<iostream>
#include<fstream>
#include <iomanip>
using namespace std;
ifstream fin("carz.in");
ofstream fout("carz.out");
int s;
double f[10002],t;
double speed(int a)
{
if (a <= 10) return 100.0;
if (a > 10 && a <= 20) return 90.0;
if (a > 20 && a <= 30) return 80.0;
if (a > 30 && a <= 40) return 75.0;
if (a > 40) return 70.0;
}
void ycl()
{
for (int i=0;i<=s;i++)
f[i]=10000.00;
}
void make()
{
fin>>s>>t;
t/=60.0;
ycl();
f[0]=0;
for (int i=0;i<=s;i+=10)
{
for (int j=0;j<i;j+=10)
{
double ans,orz;
orz=(i-j)/speed(i-j);
ans=f[j]+orz;
if (f[j]!=0) ans+=t;
if (f[i]>ans) f[i]=ans;
}
}
fout<<setiosflags(ios::fixed)<<setprecision(2)<<f[s];
}
int main()
{
make();
return 0;
}