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
  n is having_at_least_three_different_prime_divisors
  implies not n is_a_product_of_two_different_primes;
