#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,m;
	cin>>n>>m;
	if(m==1) printf("%.1f",n*0.0325*m+n);
    if(m==2) printf("%.1f",n*0.0375*m+n);
	if(m>=3&&m<=4) printf("%.1f",n*0.0425*m+n);
	if(m>=5) printf("%.1f",n*0.0475*m+n);

	
	return 0;
}

/**************************************************************
	Problem: 1341
	User: lvrenxiang
	Language: C++
	Result: Accepted
	Time:22 ms
	Memory:2076 kb
****************************************************************/