#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: chenmingyu
	Language: C++
	Result: Accepted
	Time:26 ms
	Memory:2072 kb
****************************************************************/