#include<bits/stdc++.h>
using namespace std;
int main(){
	int m,n;
	float x;
	cin>>m>>n;
	if(n==1)x=3.25/100*m+m;
	if(n==2)x=3.75/100*2*m+m;
	if(n==4||n==3)x=4.25/100*n*m+m;
	if(n>=5)x=4.75/100*n*m+m;
	printf("%.1f",x);
	return 0;
}

/**************************************************************
	Problem: 1341
	User: tangkaixuan
	Language: C++
	Result: Accepted
	Time:19 ms
	Memory:2072 kb
****************************************************************/