You are an expert Verilog hardware designer working on a complete FPGA or ASIC project. You are given the full source code of a Verilog project. One of the modules in the project is incomplete — its implementation is missing and marked with:

// >>> Module Implementation Begin

// <<< Module Implementation End

Your task is to complete the missing implementation so that the entire project functions correctly. You must infer what the missing module or logic is supposed to do by analyzing the rest of the codebase: module names, signal connections, instantiations, comments, and usage patterns.

Follow these rules:

1. Only generate Verilog code to go between the `// >>> Module Implementation Begin` and `// <<< Module Implementation End` comments.
2. Use Verilog-2001 syntax. Ensure the code is synthesizable.
3. Assume the goal is a working, integrated hardware design — your code must make the whole system function as intended.
4. Analyze the naming, I/O ports, and how the module is instantiated or used in other parts of the project.
5. Implement correct behavior based on design context. Do not guess randomly — reason it out.
6. Avoid vendor-specific features unless explicitly required.
7. Do not output comments, explanation, or anything outside the required code region unless explicitly asked.

Your output should contain **only the Verilog code** that fits inside the marked region.

/*
 * Copyright (c) 2024 Your Name
 * SPDX-License-Identifier: Apache-2.0
 */

`default_nettype none

module tt_um_secA_11_nyancar_alanz23 (
    input  wire [7:0] ui_in,    // Dedicated inputs
    output wire [7:0] uo_out,   // Dedicated outputs
    input  wire [7:0] uio_in,   // IOs: Input path
    output wire [7:0] uio_out,  // IOs: Output path
    output wire [7:0] uio_oe,   // IOs: Enable path (active high: 0=input, 1=output)
    input  wire       ena,      // always 1 when the design is powered, so you can ignore it
    input  wire       clk,      // clock
    input  wire       rst_n     // reset_n - low to reset
);

  // All output pins must be assigned. If not used, assign to 0.
 
	wire [3:0]m = ui_in[7:4];
	wire [3:0]q = ui_in[3:0];
	wire [7:0]p;

wire [2:0]carry_arr;
wire [3:0]z_out1;
wire [3:0]z_out2;
wire [3:0]z_out3;
//row 1 FA input
wire [3:0]int_sig1;
wire [3:0]int_sig1_2;

//row 1 FA output //row 2 FA input
wire [3:0]int_sig2; 
wire int_sig2_carry;
wire [3:0]int_sig2_2;

//row 2 FA output //row 3 FA input
wire [3:0]int_sig3;
wire int_sig3_carry;
wire [3:0]int_sig3_2;

and(p[0],m[0],q[0]);
and(int_sig1[0],m[1],q[0]);
and(int_sig1[1],m[2],q[0]);
and(int_sig1[2],m[3],q[0]);
and(int_sig1[3],0,0);

and(int_sig1_2[0],m[0],q[1]);
and(int_sig1_2[1],m[1],q[1]);
and(int_sig1_2[2],m[2],q[1]);
and(int_sig1_2[3],m[3],q[1]);

and(int_sig2_2[0],m[0],q[2]);
and(int_sig2_2[1],m[1],q[2]);
and(int_sig2_2[2],m[2],q[2]);
and(int_sig2_2[3],m[3],q[2]);

and(int_sig3_2[0],m[0],q[3]);
and(int_sig3_2[1],m[1],q[3]);
and(int_sig3_2[2],m[2],q[3]);
and(int_sig3_2[3],m[3],q[3]);


add_sub_4bit inst0 (.x(int_sig1), .y(int_sig1_2), .add_sub_select(1'b0), .z(z_out1), .carry_out(carry_arr[0]));
assign p[1] = z_out1[0];

assign int_sig2[0] = z_out1[1];
assign int_sig2[1] = z_out1[2];
assign int_sig2[2] = z_out1[3];
assign int_sig2[3] = carry_arr[0];

add_sub_4bit inst1 (.x(int_sig2), .y(int_sig2_2), .add_sub_select(1'b0), .z(z_out2), .carry_out(carry_arr[1]));
assign p[2] = z_out2[0];

assign int_sig3[0] = z_out2[1];
assign int_sig3[1] = z_out2[2];
assign int_sig3[2] = z_out2[3];
assign int_sig3[3] = carry_arr[1];

add_sub_4bit inst2 (.x(int_sig3), .y(int_sig3_2), .add_sub_select(1'b0), .z(z_out3), .carry_out(carry_arr[2]));

assign p[3] = z_out3[0];
assign p[4] = z_out3[1];
assign p[5] = z_out3[2];
assign p[6] = z_out3[3];
assign p[7] = carry_arr[2];

assign uo_out = p;



  assign uio_out = 0;
  assign uio_oe  = 0;

  // List all unused inputs to prevent warnings
  wire _unused = &{ena, clk, rst_n, uio_in, 1'b0};

endmodule

module one_bit_adder(
    input x,
    input y,
    input cin,
    output z,
    output cout
    );
    wire w1, w2, w3;
    assign z = x^y^cin;
    
    assign w1 = x&y;
    assign w2 = x&cin;
    assign w3 = y&cin;
    
    assign cout = w1|w2|w3;
    
endmodule

module add_sub_4bit(
    input [3:0] x,
    input [3:0] y,
    input add_sub_select,
    output [3:0] z,
    output carry_out
    );
// >>> Module Implementation Begin

// <<< Module Implementation End
endmodule





Reference solution:
rtl/generated.v:     
    wire [3:0]carry_arr;
    
    
    one_bit_adder inst0 (.x(x[0]), .y(y[0]^add_sub_select), .cin(add_sub_select), .z(z[0]), .cout(carry_arr[0]));
    
    genvar i;
    
    generate
        for (i=1; i<4; i = i+1) begin: one_bit_generate
            one_bit_adder gen_inst(.x(x[i]), .y(y[i]^add_sub_select), .cin(carry_arr[i-1]), .z(z[i]), .cout(carry_arr[i]));
        end
    endgenerate 
    assign carry_out = carry_arr[3];