var n,m,i,j,k,s1,s2:longint;
    a:array[1..16,1..16] of longint;
    
begin
//  assign(input,'input.in');
  assign(input,'flip.in');
  assign(output,'flip.out');
  reset(input);
  rewrite(output);
  read(n,m);
  for i:=1 to n do
    for j:=1 to m do read(a[i,j]);
  for i:=1 to n do begin
    s1:=0;
    s2:=0;
    for j:=1 to m do
      if a[i,j]>=0 then s1:=s1+a[i,j]
      else s2:=s2-a[i,j];
    if s2>s1 then 
      for j:=1 to m do
        a[i,j]:=-a[i,j];
  end;
  for i:=1 to m do begin
    s1:=0;
    s2:=0;
    for j:=1 to n do
      if a[j,i]>=0 then s1:=s1+a[j,i]
      else s2:=s2-a[j,i];
    if s2>s1 then 
      for j:=1 to n do
        a[j,i]:=-a[j,i];
  end;
  for i:=1 to n do
    for j:=1 to m do
      k:=k+a[i,j];
  writeln(k);
end.