reserve a,b,c,d,x,j,k,l,m,n,o,xi,xj for Nat,
  p,q,t,z,u,v for Integer,
  a1,b1,c1,d1 for Complex;

theorem
  for p be prime Nat, a be non trivial Nat holds
    a |-count p <= 1
proof
  let p be prime Nat, a be non trivial Nat;
  a > 1 by Def0; then
  a |-count p = 0 or a = p by NAT_3:24;
  hence thesis by Def0,NAT_3:22;
end;
