Miért nem megy ez a program free pascalban?

var sz1,sz2:char;

t1,t2,t3:array[1..255] of 0..9;

h1,h2,mb1,mb2,i1,i2,j1,j2,j3,j4,j5,s1,s2,s3:integer;

begin

i1:=0;i2:=0;s1:=0;s2:=0;s3:=0;

repeat

sz1:=readkey;

if sz1<>#13 then begin

inc(i1);

val(sz1,mb1,h1);

t1[i1]:=mb1;

end

until sz1=#13;

for j1:=1 to i1 do

t1[255-i1+j1]:=t1[j1];

repeat

sz2:=readkey;

if sz2<>#13 then begin

inc(i2);

val(sz2,mb2,h2);

t2[i2]:=mb2;

end

until sz2=#13;

for j2:=1 to i2 do

t2[255-i2+j2]:=t2[j2];

for j3:=255 downto 1 do begin

s1:=t1[j3]+t2[j3]+s3;

s2:=s1 mod 10;

s3:=s1 div 10;

t3[j3]:=s2;

end;

if i1>i2 then

for j4:=(255-inc(i1)) to 255 do

write(t3[j4]);

else for j5:=(255-inc(i2)) to 255 do

write(t3[j5]);

end.