var i,j,n,m,k:byte;
    a:array [1..16,1..16] of longint;
    s:array [1..32] of longint;
    suma:longint;
    f:text;
begin
  assign(f,'flip.in');
  reset(f);
  read(f,n);readln(f,m);
  for i:=1 to n do for j:=1 to m do read(f,a[i,j]);
  close(f);
  for i:=1 to n do begin
                       s[i]:=0;
                       for j:=1 to m do s[i]:=s[i]+a[i,j];
                       if s[i]<0 then for j:=1 to m do a[i,j]:=a[i,j]*(-1);
                   end;
  k:=n+1;
  for j:=1 to m do begin
                      s[k]:=0;
                      for i:=1 to n do s[k]:=s[k]+a[i,j];
                      if s[k]<0 then for i:=1 to n do a[i,j]:=a[i,j]*(-1);
                      k:=k+1;
                   end;
  suma:=0;
  for i:=1 to n do for j:=1 to m do suma:=suma+a[i,j];
  assign(f,'filp.out');
  rewrite(f);
  write(f,suma);
  close(f);
end.