function L = digraph_arc_abcd ( )

%*****************************************************************************80
%
%% digraph_arc_abcd() returns the arc list for a 4-node example.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    25 April 2026
%
%  Author:
%
%    John Burkardt
%
%  Output:
%
%    integer L(5,2), the arc list.
%
  arc_num = 5;

  L = [ ...
    1, 2; ...
    2, 3; ...
    3, 1; ...
    3, 4; ...
    4, 1 ];

  return
end
