var a:array[1..16,1..16] of longint;
  i,j,k,m,N,r:byte; pos,neg:longint;  F;text;
begin
 assign(F, 'flip.in');
 reset(F);
 readln(F, N,M);
  for i:=1 to N do begin
   for j:=1 to M do
     readln(F, a[i,j]);
    readln(F);
   end;
 close(F);
 for i:=1 to N do begin
  neg:=0; pos:=0;
  for j:=1 to M do
   if a[i,j]<0 then neg:=neg+a[i,j]
    else pos:=pos+a[i,j];
   if abs(neg)>pos then
     for  j:=1 to M do
       a[i,j]:=a[i,j]*-1;
    neg:=0; pos:=0;
   for r:=1 to M do  begin
  for k:=1 to N do
   if a[k,m]<0 then neg:=neg+a[k,r]
    else pos:=pos+a[k,r];
  if abs(neg)>pos then
    for k:=1 to N do
    a[k,r]:=a[k,r]*-1;
  end;
end;
 pos:=0;
 for i:=1 to N do
  for j:=1 to M do
     pos:=pos+a[i,j];
  assign(F, 'Flip.out');
  rewrite(F);
  writeln(F, pos);
  close(F);
 end.