#include<iostream>
#include<iomanip>
using namespace std;
class fuel{
    public:
    virtual void total(float q,float p){
        cout<<q*p;
    }
};
class fuelcost : public fuel{
    public:
    void total(float q,float p){
        cout<<fixed<<setprecison(2)<<q*p;
    }
};
int main(){
    fuelcost obj;
    string  s;
    cin>>s;
    float q,p;
    cin>>q>>p;
    if(s=="petrol" || s=="diesel" &&(q>0 && p>0)){
        obj.total(q,p);
        
    }
    else{
        cout<<"Invalid input;"
    }
}