// editor1
#include<iostream>
using namespace std;
class Customer{
    protected:
    string name;
    public:
    void display()
    {
        cin>>name;
    }
};
class Meter{
    protected:
    int n;
    public:
    void display()
    {
        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.display();b.displat1();b.res();
  return 0;
}