#include<iostream>
#include<string>
using namespace std;
class customer
{
    protected:
    string name;
    public:
    void display()
    {
        cin >> name;
    }
};
class meter{
    protected:
    int n;
    public:
    void display1()
    {
        cin >> n;
    }
};
class Bill : public Meter , public Customer
{
    public:
    void res()
    {
        if(n<0)
        {
            cout << "Invalid input"<<endl;
            return 0;
        }
        int total = (n*S)+50;
        cout << total <<endl;
    }
};
int main()
{
    Bill b();
    b.display();b.display1();b.res();
    return 0;
}