#include<bits/stdc++.h>
using namespace std;
int main(){
    int n ,m ;
    double s;
    cin>>n>>m;
    if(m==1){
        s=n*0.0325*m+n;
    }else if (m==2){
        s=n*0.0375*m+n;
    }else if (m==3 || m==4){
        s=n*0.0425*m+n;
    }else{
        s=n*0.0475*m+n;
    }
    printf("%.1f",s); 
}
/**************************************************************
	Problem: 1341
	User: yangjunwen
	Language: C++
	Result: Accepted
	Time:21 ms
	Memory:2072 kb
****************************************************************/