I cannot see the proper solution where we inherit all methods. So, here it is:

class BadLengthException : public exception {
private:
    string message;
public:
    BadLengthException(const int& msg) : message(to_string(msg)) {}
    const char* what() const noexcept override{
        return message.c_str();
    }
};

To be syntactically coherent with error messages, we need to return the error as a C-style string, not an integer.

what defines if something is invalid???

try c++14 class BadLengthException : public exception{ private: int length; public: BadLengthException(int n){ length=n; } int what(){ return length; } };

How could i know if it valid or not valid or short ??????

when im trying to solve the code in c++20 im not receiving any prior code, how do i fix this can someone please help me out