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];
    for k:=1 to m do begin
      s1:=0;
      s2:=0;
      for j:=1 to n do
        if a[j,k]>=0 then s1:=s1+a[j,k]
        else s2:=s2-a[j,k];
      if s2>s1 then
        for j:=1 to n do
          a[j,k]:=-a[j,k];
    end;
  end;
  k:=0;
  for i:=1 to n do
    for j:=1 to m do
      k:=k+a[i,j];
  writeln(k);
end.