#include<bits/stdc++.h>
using namespace std;
double money;
int main(){
     int n;
     float m;
     cin>>n>>m;
     if(n<=40){
          money=m*n;
     }else if(n<=50){
          money=40*m+(n-40)*1.5*m;
     }else{
          money=55*m+(n-50)*2*m;
     }
     cout << fixed << setprecision(2) <<money;;
     return 0;
}