module COMBO ( Cin1, Cin2, sel, Cout );
  input [4:0] Cin1, Cin2;
  input sel;
  output [4:0] Cout;
  reg [4:0] Cout;

  wire   [4:0] arth_o;

  ARITH U2_ARITH ( .a(Cin1), .b(Cin2), .sel(sel), .out1(arth_o) );

always @ (Cin1, arth_o)
  begin
    Cout <= arth_o + Cin1;
  end

endmodule