program joculflip;
var a:array[1..16,1..16]of longint;
    n,i,j,m:integer;
    s:longint;
    f:text;
begin
 assign(f,'flip.in');
 reset(f);
 read(f,n,m);
 for i:=1 to n do
  for j:=1 to m do
   read(f,a[i,j]);
{  for i:=1 to n do
   begin
   for j:=1 to m do
    write(a[i,j]:3);
   writeln;
  end;
  writeln;   }
 close(f);
 assign(f,'flip.out');
 rewrite(f);
  for j:=1 to m do
  begin
   s:=0;
   for i:=1 to n do
    s:=s+a[i,j];
   if s<0 then
    for i:=1 to n do
     a[i,j]:=-a[i,j];
  end;
 for i:=1 to n do
  begin
   s:=0;
  for j:=1 to m do
   s:=a[i,j]+s;
  if s<0 then
   for j:=1 to m do
    a[i,j]:=-a[i,j];
  end;

{  for i:=1 to n do
   begin
   for j:=1 to m do
    write(a[i,j]:3);
   writeln;
  end;
  writeln;             }
 s:=0;
 for i:=1to n do
  for j:=1 to n do
   s:=s+a[i,j];
 write(f,s);
close(f);
end.