#include<cstdio>
using namespace std;
double f[10006],sped[10006];
int s,T;
int main(){
	freopen("carz.in","r",stdin);
	freopen("carz.out","w",stdout);
	scanf("%d%d",&s,&T);
	sped[0]=0.00; sped[10]=100.00;
	sped[20]=90.00; sped[30]=80.00;
	sped[40]=75.00;
	for(int i=50;i<=s;i+=10) sped[i]=70.00;
	for(int i=10;i<=s;i+=10){
		f[i]=10000000.00;
		for(int j=0;j<=i-10;j+=10){
			double charge=f[j]+(double)(i-j)/sped[i-j]+T;
			if(charge<f[i]) f[i]=charge;
		}
	}
	printf("%.2lf",f[s]-T);
//	getchar();getchar();
	return 0;
}