65. Ripple Carry Adder

How do you plan to solve it?

// 1-bit Full Adder (to be used by the 4-bit RCA)
module full_adder_1bit (
    input  a, b, cin,
    output sum, cout
);
    assign sum=a^b^cin;
    assign cout=a&b|b&cin|cin&a;

endmodule

// 4-bit Ripple Carry Adder – chain 4 full adders
module rca4_chain (
    input  [3:0] a,
    input  [3:0] b,
    input        cin,
    output [3:0] sum,
    output       cout
);
wire w[2:0];
    full_adder_1bit h1(a[0],b[0],cin,sum[0],w[0]);
    full_adder_1bit h2(a[1],b[1],w[0],sum[1],w[1]);
    full_adder_1bit h3(a[2],b[2],w[1],sum[2],w[2]);
    full_adder_1bit h4(a[3],b[3],w[2],sum[3],cout);

endmodule