#include<stdio.h>
int main(){
	int n;
	double m,s=0.0;
	scanf("%d%lf",&n,&m);
	if(n<=40) s=n*m;
	if(n>40 && n<=50) s=40*m+(n-40)*1.5*m;
	if(n>50) s=40*m+15*m+(n-50)*2*m;
	printf("%.2f",s);
	return 0;
}
/**************************************************************
	Problem: 1860
	User: admin
	Language: C
	Result: Accepted
	Time:75 ms
	Memory:1144 kb
****************************************************************/