module top_module(
   input [ 399: 0 ] a, b,
   input cin,
   output cout,
   output [ 399: 0 ] sum );
wire [ 99: 0 ] temp_co;
genvar i;
generate
    for ( i = 0; i < 100 ; i = i + 1 )
    begin:ppp
        if ( i == 0 )
            bcd_add bcd_add_inst( a[ i * 4 + 3 : i * 4 ], b[ i * 4 + 3 : i * 4 ], cin, temp_co[ i ], sum[ i * 4 + 3 : i * 4 ] );
        else
            bcd_add bcd_add_inst( a[ i * 4 + 3 : i * 4 ], b[ i * 4 + 3 : i * 4 ], temp_co[ i - 1 ], temp_co[ i ], sum[ i * 4 + 3 : i * 4 ] );
    end
endgenerate

assign cout = temp_co[ 99 ];

endmodule


module bcd_add(
    input [ 3: 0 ] x,
    input [ 3: 0 ] y,
    input ci,

    output co,
    output reg [ 3: 0 ] sum
);
wire [ 4: 0 ] temp = x + y + ci;
always @ ( * )

    if ( temp >= 10 )
    begin
        sum = temp - 10;
        co = 1;
    end
    else
    begin
        sum = temp;
        co = 0;
    end


endmodule