#include<iostream>
#include<iomanip>
#include<string>
using namespace std;
class QuantityCalculation
{
    protected:
    string name;
    float quan, price;
    float res=0;
    public:
    void quantity(string name, float quan, float price)
    {
        res=quan*price;
    }
    void quantity()
    {
        if(res<0)
        {
            cout<<"Invalid input"<<endl;
            return;
        }
        else
        {
            cout<<fixed<<setprecision(2)<<res;
        }
    }
};
int main()
{
    string name;
    float quan, price;
    cin>>name>>quan>>price;
    if(quan<0||price>0||(name!="petrol"&&name!="diesel")
    {
        cout<<"Invalid input";
        return 0;
    }
    QuantityCalculation q;
    q.quantity(name,quan, price);
    q.quantity();
    return 0;
}