#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,m;
	cin>>n>>m;
	if(m==1) cout<<fixed<<setprecision(1)<<n*0.0325*m+n;
	if(m==2) cout<<fixed<<setprecision(1)<<n*0.0375*m+n;
	if(m==3||m==4) cout<<fixed<<setprecision(1)<<n*0.0425*m+n;
	if(m>=5) cout<<fixed<<setprecision(1)<<n*0.0475*m+n;
	return 0;
}
/**************************************************************
	Problem: 1341
	User: linmiaoling
	Language: C++
	Result: Accepted
	Time:22 ms
	Memory:2072 kb
****************************************************************/