#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
int S;
double f[10005],T,speed[10005]={0,100,90,80,75,70};
int Main() {
	freopen("carz.in","r",stdin);
	freopen("carz.out","w",stdout);
	scanf("%d%lf",&S,&T);
	S/=10,T/=60;
	memset(f,0x5f,sizeof(f)),f[0]=-T;
	for(int i=6; i<=1000; ++i) speed[i]=70;
	for (int i=1; i<=S; ++i) {
		for (int j=i-1; j>=0; j--) {
			double temp=f[j]+double((i-j)*10)/(speed[i-j])+T;
			if (temp<f[i]) f[i]=temp;
		}
	}
	printf("%0.2lf",f[S]);
	return 0;
}
int hehe=Main();
int main(){;}