type matrice=array[1..50,1..50]of integer;
var f,g:text;
    a:matrice;
    m,n,i,j:integer;
function calcul(var a:matrice):integer;
var s1,s2:integer;
begin
s2:=0;
 for i:=1 to n do begin
  s1:=0;
  for j:=1 to m do
  s1:=s1+a[i,j];
  if s1<0 then begin
   for j:=1 to m do
    a[i,j]:=a[i,j]*(-1);
       end;
  end;
 for j:=1 to m do begin
  s1:=0;
   for i:=1 to n do
   s1:=s1+a[i,j];
   if s1<0 then begin
    for i:=1 to n do
     a[i,j]:=a[i,j]*(-1);
      end;
  end;s2:=0;
for i:=1 to n do
 for j:=1 to n do
  s2:=s2+a[i,j];
  calcul:=s2;
end;
begin
assign(f,'flip.in');reset(f);
assign(g,'flip.out');rewrite(g);
read(f,n);
read(f,m);
for i:=1 to n do begin
 for j:=1 to m do
  read(f,a[i,j]);
  readln(f);
  end;
write(g,calcul(a));
close(g);
write(calcul(a));
end.