#include <iostream>

class cAccount {
private:
    unsigned long long accountId;
    double accountBalance;

public:
    cAccount(unsigned long long id, double balance = 0.0):
        accountId{ id }, accountBalance{ balance } { }
    ~cAccount() = default;

    unsigned long long id() const {
        return accountId;
    }

    double balance() const {
        return accountBalance;
    }

    double balance(double newBalance) {
        if (newBalance >= 0.0)
            accountBalance = newBalance;
        return accountBalance;
    }
};

int main() {

    cAccount acc(1263721);
    cAccount bcc(1273812);

    bcc.balance(72);
    acc.balance(bcc.balance);

    std::cout << acc.id() << " has " << acc.balance() << "\n";
    std::cout << bcc.id() << " has " << bcc.balance() << "\n";

}