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