69. Binary Subtractor

How do you plan to solve it?

/*Write your code here*/
module sub4_2c(
    input [3:0] a,
    input [3:0] b,
    output [3:0] diff,
    output bout
);
wire [4:0] sum = {1'b0,a} + {1'b0, ~b} + 5'b00001;
assign diff = sum [3:0];
assign bout = ~sum [4];


endmodule