Creating a class member that is automatically calculated from other class members?

1. I'm an absolute newbee when it comes to programming and I'm trying to teach myself the basics by just solving some easy "problems" in C++.

2. I have searched the web for an exact answer to my question before posting it here and haven't found one so far, however that may be because of (1).

So, what I'm looking for is a way to declare a class member that gets automatically calculated from other members of the same class, so that the calculated class member can be used just like an explicitly defined class member would. For example imagine a struct called creature that has the properties/members creature.numberofhands, creature.fingersperhand and finally the property creature.totalfingers that automatically gets calculated from the above members.

Heres an example of the closest I got to what I wanted to achieve:

#include <iostream>

typedef struct creature {
    int numberofhands;
    int fingersperhand;
    int totalfingers();
} creature;    

int creature::totalfingers()
{
    return numberofhands * fingersperhand;
};

int main()
{
    creature human;
    human.numberofhands = 2;
    human.fingersperhand = 5;

    printf("%d",human.totalfingers());
    return(0);
}

What's really annoying me about this, is that I have to treat the calculated one DIFFERENTLY from the explicitly defined ones, i.e. I have to put "()" after it. How can I change the code, so I can use: human.totalfingers without ever explicitly defining it?