Differ first and following

[Mike92]

Hi guys I am stuck with an issue as I need to come up with a code such that the first time run it requires only a number and the following will be a number and operation. I am done with the second half but I have totally no idea how to create a code just for the first time just the number. Can I have any clues how to start please.
Thank you

[48T7M4Gy]

?

[Mike92]

I have to create a function in class called void getCommand where I have to request a number for the first time and request a operation (+,-,/or *) then a number for the following

[48T7M4Gy]

void getCommand()
{
    some code here ...
}