// editor1
#include<iostream>
#include<iomanip>
usin 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<<setprecision(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";
    }
    return 0;
}