Подсчет суммы шестнадцатеричных чисел

var s1,s2,s:string;
    a,b,c:array[byte] of integer;
    n,m,i,j,p,k:integer;
begin
repeat
p:=0;
write('Введите число A в СС 16:');
readln(s1);
s1:=uppercase(s1);
i:=1;
while(i<=length(s1))and(p=0) do
if not(s1[i] in ['0'..'9','A'..'F']) then p:=1
else i:=i+1;
until p=0;
repeat
p:=0;
write('Введите число B в СС 16:');
readln(s2);
s2:=uppercase(s2);
i:=1;
while(i<=length(s2))and(p=0) do
if not(s2[i] in ['0'..'9','A'..'F']) then p:=1
else i:=i+1;
until p=0;
if length(s1)<length(s2) then
while length(s1)<length(s2) do
s1:='0'+s1
else if length(s1)>length(s2) then
while length(s2)<length(s1) do
s2:='0'+s2;
writeln('  ',s1);
writeln(' +');
writeln('  ',s2);
for i:=1 to length(s1)+2 do
write('-');
writeln;
n:=length(s1);
m:=n;
for i:=1 to n do
 begin
  if s1[i] in ['0'..'9'] then  a[i]:=ord(s1[i])-48
  else a[i]:=ord(s1[i])-55;
  if s2[i] in ['0'..'9'] then  b[i]:=ord(s2[i])-48
  else b[i]:=ord(s2[i])-55;
 end;
p:=0;
for i:=n downto 1 do
  begin
   c[i]:=a[i]+b[i]+p;
   if (c[i]>15)and(i>1) then
      begin
       c[i]:=c[i] mod 16;
       p:=1;
      end
    else p:=0;
  end;
if c[1]>15 then
  begin
    c[1]:=c[1] mod 16;
    n:=n+1;
    for j:=n downto 2 do
    c[j]:=c[j-1];
    c[1]:=1;
  end;
if n=m then write('  ')
else write(' ');
for i:=1 to n do
if c[i] in [0..9] then write(c[i])
else write(chr(c[i]+55));
writeln;
s:='';
for i:=1 to n do
if c[i]<10 then s:=s+chr(c[i]+48)
else s:=s+chr(c[i]+55);
s:='$'+s;
val(s,p,k);
writeLn('В СС 10=',p)
end.