// editor1
#include <iostream>
#include<iomanip>
#include<string>
using namespace std;
class qty{
    public:
    float quan,price;
    float res;
    string fuel;
    void qtyy(float quan, float price,string fuel){
     if (fuel!=="petrol" || fuel!=="diesel"){
         cout<<"Invalid input";
     }
        if (quan<0 || price<0){
        cout<<"Invalid input";
    }
        res=quan*price;
        cout<<fixed<<setprecision(2)<<res;
    }
};
int main(){
    string fuel;
    float quan, price;
    cin>>fuel;
    cin>>quan>>price;
    qty q;
    q.qtyy(quan,price,fuel);
    return 0;
}