reserve d,i,j,k,m,n,p,q,x,k1,k2 for Nat,
  a,c,i1,i2,i3,i5 for Integer;

theorem
  for p being Nat holds p > 2 & p is prime implies p is odd
proof
  let p be Nat;
  assume
A1: p > 2 & p is prime;
  assume p is even;
  then p mod 2 = 0 by NAT_2:21;
  then ex k being Nat st p = 2*k + 0 & 0 < 2 by NAT_D:def 2;
  then 2 divides p;
  hence contradiction by A1,INT_2:def 4;
end;
