выдает ошибку,а работает только при n>числа компонент файла

 program lab4;
type
TV=array[1..10] of real;
TF=file of real;
var
B:TV;
F:TF;
n,i,k:byte;
s,p:real;
bool:boolean;
procedure vvodF(var H:TF;name:char);
var
a:real;
begin
rewrite(H);
writeln('priznak konza vvoda- 999');
writeln('vvedite novoe chislo');
readln(a);
while a<>999 do
begin
write(f,a);
writeln('vvedite ocherednoe chislo');
read(a);
end;
close(f);
end;
function Pr(var f:TF;n:integer):real;
var
a,p:real;
begin
reset(f);
p:=1;
k:=0;
while not eof(f) or (k<>n) do
begin
read(f,a);
if a<>0 then
begin
p:=p*a;
k:=k+1
end
end;
if k=n then
pr:=p
else
begin
writeln('nevozmozhno podschitat proizvedenie');
pr:=0;
end;
close(f);
end;
function sum(var f:TF;n:integer):real;
var
a,s:real;
i:byte;
begin
reset(f);
s:=0;
seek(f,filesize(f)-1);
for i:=1 to n do
begin
read(f,a);
s:=s+a;
seek(f,filepos(f)-2);
end;
sum:=s;
close(f);
end;
function FormV(var f:TF;x:TV;s,p:real):boolean;
var
a:real;
i:byte;
begin
reset(f);
if filesize(f)>7 then
begin
for i:=1 to 8 do
begin
read(f,a);
x[i]:=a;
end;
x[9]:=s;
x[10]:=p;
bool:=true
end 
else
begin
writeln('nevozmozhno sformirovat vector');
bool:=false;
end;
close(f);
end;
procedure PrintV(const x:TV);
var
i:byte;
begin
for i:=1 to 9 do
writeln('x[',i,']=',x[i]);
if x[10]= 0 then
else
writeln(x[i]);
end;
 
BEGIN
assign(f,'f.dat');
vvodF(f,'f');
write('n=');
readln(n);
reset(f);
if filesize(f)<n then
begin
writeln('nevozmozhno podschitat summy/proizvedenie');
p:=0;
end
else
begin
p:=pr(f,n);
s:=sum(f,n);
end;
bool:=formV(F,b,s,p);
if bool then
printV(b);
END.