Write a function named computeGCD that takes two positive integer arguments and returns the greatest common divisor of those two integers. If the function is passed an argument that is not greater than zero, then the function should return the value -1 to indicate than an error occurred. For instance,

(THE COUT IS JUST AN EXAMPLE FOR THE GENERAL FORMAT. THE HOMEWORK PROBLEM SPECIFIES THAT YOU WRITE A FUNCTION NAMED GCD THAT TAKES TWO INTERGERS INPUTED BY THE USER AND TAKES THE GREATEST COMMON DIVISOR FROM THEM. DO NOT JUST USE THE EXAMPLE AS THE FUNCTION.) [4] cout << computeGCD(8, 12); // output: 4 cout << computeGCD(256, 625); // output: 1 cout << computeGCD(0, 8); // output: -1 cout << computeGCD(10, -2); // output: -1