Why I received WA?

My Program in Pascal:

Program P1036;
Type TNum=Array[0..52] of Byte;
     TList=Array[1..2,0..450] of TNum;
Var A,C:TList;
    B:TNum;
    n,s,i,j,k:Integer;

Procedure Add(A:TNum; Var B:TNum);
Var p,i:Byte;
Begin
  if B[0]<A[0] then B[0]:=A[0];
  p:=0;
  for i:=1 to B[0] do
    begin
      inc(p,A[i]+B[i]);
      B[i]:=p mod 100;
      p:=p div 100
    end;
  if p<>0 then begin
                 inc(B[0]); B[B[0]]:=p
               end
End;

Procedure Out(A:TNum);
Var i:Byte;
Begin
  write(A[A[0]]);
  for i:=A[0]-1 downto 1 do
    if A[i]>=10 then write(A[i]) else write('0',A[i]);
  writeln
End;

Procedure SqrNum(B:TNum; Var C:TNum);
Var i,j:Byte;
    p:Longint;
Begin
  fillchar(C,sizeof(C),0); C[0]:=B[0]*2;
  for i:=1 to B[0] do
    if B[i]<>0 then
      begin
        p:=0;
        for j:=1 to B[0] do
          begin
            inc(p,Longint(B[i])*B[j]+C[i+j-1]);
            C[i+j-1]:=p mod 100;
            p:=p div 100
          end;
        if p<>0 then inc(C[i+B[0]],p)
      end;
  if C[C[0]]=0 then dec(C[0])
End;

Begin
  readln(n,s);
  if (s<0) or odd(s) then begin writeln(0); halt end;
  s:=s div 2;
  if s>n*9 then begin writeln(0); halt end;
  if (s=0) or (s=n*9) then begin writeln(1); halt end;
  if s=1 then begin writeln(n*n); halt end;
  fillchar(A[1],sizeof(A[1]),0);
  for i:=0 to 9 do begin A[1,i,1]:=1; A[1,i,0]:=1 end;
  for i:=2 to n do
    begin
      fillchar(A[2],sizeof(A[2]),0);
      for j:=0 to 9 do
        for k:=0 to 9*i-9 do
          if j+k<=s then Add(A[1,k],A[2,j+k]);
      A[1]:=A[2]
    end;
  SqrNum(A[2,s],B);
  Out(B)
End.

The "add" procedure is obviously wrong.
the "p" variable there is not initialized.
"i" is never used.
And what the hell "b[0]0" does mean? May be "b[0]=0"?


> Why I received WA?
>
> My Program in Pascal:
>
> Program P1036;
> Type TNum=Array[0..52] of Byte;
>      TList=Array[1..2,0..450] of TNum;
> Var A,C:TList;
>     B:TNum;
>     n,s,i,j,k:Integer;
>
> Procedure Add(A:TNum; Var B:TNum);
> Var p,i:Byte;
> Begin
>   if B[0]<A[0] then B[0]:=A[0];
>   p:=0;
>   for i:=1 to B[0] do
>     begin
>       inc(p,A[i]+B[i]);
>       B[i]:=p mod 100;
>       p:=p div 100
>     end;
>   if p<>0 then begin
>                  inc(B[0]); B[B[0]]:=p
>                end
> End;
>
> Procedure Out(A:TNum);
> Var i:Byte;
> Begin
>   write(A[A[0]]);
>   for i:=A[0]-1 downto 1 do
>     if A[i]>=10 then write(A[i]) else write('0',A[i]);
>   writeln
> End;
>
> Procedure SqrNum(B:TNum; Var C:TNum);
> Var i,j:Byte;
>     p:Longint;
> Begin
>   fillchar(C,sizeof(C),0); C[0]:=B[0]*2;
>   for i:=1 to B[0] do
>     if B[i]<>0 then
>       begin
>         p:=0;
>         for j:=1 to B[0] do
>           begin
>             inc(p,Longint(B[i])*B[j]+C[i+j-1]);
>             C[i+j-1]:=p mod 100;
>             p:=p div 100
>           end;
>         if p<>0 then inc(C[i+B[0]],p)
>       end;
>   if C[C[0]]=0 then dec(C[0])
> End;
>
> Begin
>   readln(n,s);
>   if (s<0) or odd(s) then begin writeln(0); halt end;
>   s:=s div 2;
>   if s>n*9 then begin writeln(0); halt end;
>   if (s=0) or (s=n*9) then begin writeln(1); halt end;
>   if s=1 then begin writeln(n*n); halt end;
>   fillchar(A[1],sizeof(A[1]),0);
>   for i:=0 to 9 do begin A[1,i,1]:=1; A[1,i,0]:=1 end;
>   for i:=2 to n do
>     begin
>       fillchar(A[2],sizeof(A[2]),0);
>       for j:=0 to 9 do
>         for k:=0 to 9*i-9 do
>           if j+k<=s then Add(A[1,k],A[2,j+k]);
>       A[1]:=A[2]
>     end;
>   SqrNum(A[2,s],B);
>   Out(B)
> End.
>
>