procedure A is
    N    : Unsigned_32;
    Encr : Block;
  begin
    X := X + 1;
    Encrypt(KS, Plain, Encr);
    Plain := Encr;

    if X <= Max then
      N := MT.Gen_U32;
      if N mod 3 = 0 then
        B; C;
      elsif N mod 3 = 1 then
        B;
      else
        C;
      end if;
    end if;
    exception
      when E1 => 
        Y := Y + 10;
  end A;