Сортировка чисел в файле

[vadiprog]

program Project3;

{$APPTYPE CONSOLE}

uses SysUtils;
var f:file of integer;
a,b,i,j,x:integer;
begin
assign(f,'Chisla.txt');
rewrite(f);
writeln('Vvedit chisla, dlia zakinchenia vvedit 0:');
repeat
readln(a);
write(f,a);
until a=0;
writeln('Pochatkovii fail:');
reset(f);
while not eof(f) do
begin
read(f,a);
write(a,' ');
end;
writeln;
close(f);
reset(f);
for i:=0 to filesize(f)-2 do
for j:=i+1 to filesize(f)-1 do
begin
seek(f,i);
read(f,a);
seek(f,j);
read(f,b);
if a<b then
begin
x:=a;
a:=b;
b:=x;
seek(f,i);
write(f,a);
seek(f,j);
write(f,x);
end;
end;
close(f);
writeln('Vidsortovanii fail:');
reset(f);
while not eof(f) do
begin
read(f,a);
write(a,' ');
end;
close(f);
readln
end.



Как вот тут
for i:=0 to filesize(f)-2 do
for j:=i+1 to filesize(f)-1 do
убрать -2 и -1