#include <stdio.h>
void main()
{
	int n,m;
	double p;
	scanf("%d %d",&n,&m);
	if(m>=5)
	{
		p=n*0.0475*m+n;
	}else if(m==3||m==4){
		p=n*0.0425*m+n;
	}else if(m==2){
		p=n*0.0375*m+n;
	}else if(m==1){
		p=n*0.0325*m+n;
	}
	printf("%.1f",p);
	  
}
/**************************************************************
	Problem: 1341
	User: admin
	Language: C
	Result: Accepted
	Time:23 ms
	Memory:1144 kb
****************************************************************/