#include <iostream>   
#include <cstdio>   
#include <cstdlib>   
#include <cmath>   
#include <cstring>   
#include <string>   
#include <algorithm>   
#include <iomanip>   
using namespace std;  
int d,e,k;
double a,b,c,s=0,f[20000],r[3]={80,75,70};
int main(void)   
{   
    freopen ("carz.in","r",stdin);   
    freopen ("carz.out","w",stdout);   
	cin>>a>>b;
	b=(double)(b/60);
	f[1]=0.1;
	f[2]=0.2+b<(double)((double)2/9)?0.2+b:(double)((double)2/9);
	for (d=3;d<=a/10;d++)
	{
		if (d>=5) k=2;
			else k=d-3;
		f[d]=d*10/r[k];
		for (e=1;e<=d/2;e++)
			if (f[e]+f[d-e]+b<f[d]) f[d]=f[e]+f[d-e]+b;
	}
	printf("%.2lf",f[d-1]);
    fclose(stdin);   
    fclose(stdout);   
    return 0;   
}