var   A : array[0 .. 17, 0 .. 17] of longint;
   rows, i, cols, j, N, M: integer;   F:text;
   s, max : int64;
   minusi, minusj : integer;
begin
   max :=0;
   assign(F, 'flip.in');
   reset(F);
   readln(F, N, M);
    for i:=0 to N-1 do  begin
     for j:=0 to M-1 do
      read(F, a[i,j]);
     readln(F);
    end;
    close(F);
   for rows := 0 to Pred (1 shl N) do
   begin
      for cols := 0 to Pred(1 shl M) do
      begin
         s := 0;
         for i := 0 to Pred(N) do
         begin
            for j := 0 to Pred(M) do
            begin
               minusi := 1 - 2 * ((rows shr i) and $1);
               minusj := 1 - 2 * ((cols shr j) and $1);
               s := s + A[i, j] * minusi * minusj;
            end;
         end;
        if s > max then max := s;
      end;
   end;
   assign(F, 'flip.out');
   rewrite(F);
   writeln(F, max);
   close(F);
 end.