Given a sequence of CW complexes K(Gn,n), n=1,2,⋯, let Xn be the CW complex formed by the product of the first n of these K(Gn,n)'s. Via the inclusions Xn−1⊂Xn coming from regarding Xn−1 as the subcomplex of Xn with nth coordinate equal to a basepoint 0-cell of K(Gn,n), we can then form the union of all the Xn's, a CW complex X. Show πn(X)≈Gn for all n.