package Simple_Greatest_Common_Divisor
is

   --# function Gcd (A, B : Natural) return Natural;

   procedure G_C_D (M, N : in Natural; G : out Natural);
     --# derives G from M, N;
     --# pre N > 0;
     --# post G = Gcd (M, N);

end Simple_Greatest_Common_Divisor;