#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;
        }
        int total = (n*5)+50;
        cout<<total<<endl;
    }
};
int main()
{
    Bill b;
    b.display1();b.display1();b.res();
    return 0;
}