reserve X for set;
reserve a,b,c,k,m,n for Nat;
reserve i,j for Integer;
reserve r,s for Real;
reserve p,p1,p2,p3 for Prime;
reserve z for Complex;

theorem
  a <> 1 & a <> n & a is non prime & a divides n implies
  n is not_a_product_of_two_primes by GR_CY_3:1;
