For three positive integers \(p,q,r,x^{pq^{2}} = y^{qr} = z^{p^{2}r}\) and \(r = pq + 1\) such that \(3,3\log_{y}x,3\log_{z}y,7\log_{x}z\) are in A.P. with common difference \(1/2\). The \(r - p - q\) is equal to\\