#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<<setprecision(2)<<q*p;
    }
};
int maon()
{
    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;
}