#include<stdio.h>
#define INF 1000000000
using namespace std;
double D[2000]={0};
double v[2000]={0};
int main()
{
	freopen("carz.in","r",stdin);
	freopen("carz.out","w",stdout);
	int s,a;
	scanf("%d%d",&s,&a);
	double t=double(a)/60;//s是路程，t是时间。
	v[0]=t;
	v[1]=double(10)/double(100)+t;
	v[2]=double(20)/double(90)+t;
	v[3]=double(30)/double(80)+t;
	v[4]=double(40)/double(75)+t;
	for (int i=5;i<=10000/10;i++)
		v[i]=(i*10)/double(70)+t;
	for (int i=1;i<=s/10;i++) D[i]=INF;
		
	for (int i=1;i<=s/10;i++)
		for (int j=i;j<=s/10;j++)
			if (D[j]>D[j-i]+v[i]) D[j]=D[j-i]+v[i];
	printf("%.2lf",D[s/10]-t);
}