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