program flip;
type matrice =array [1..16,1..16] of integer;
var a,b,suma:longint;
 v :matrice;
 m,n,i,k,j:shortint;
fin,fout:text;
begin
assign(fin,'flip.in');
assign(fout,'flip.out');
reset(fin);
rewrite(fout);
read(fin,n,m);readln(fin);



for i:=1 to n do   begin

for j:=1 to m do     begin
                     read (fin,v[i,j]);
                      end;
                      readln(fin);
                      end;

for i:=1 to n do   begin
                        suma:=0;
for j:=1 to m do     begin
                    suma:=suma+v[i,j];
                    if suma< 0  then   begin
                                         for k:=1 to m  do  begin v[i,k] := -v[i,j];end;
                                        end;
                      end;

                      end;


for j:=1 to m do   begin

                        suma:=0;
for i:=1 to n do     begin
                    suma:=suma+v[i,j];
                    if suma< 0   then begin
                                        for k:=1 to n do  begin v[k,j]:=- v[i,j];end;
                                   end;
                      end;

                      end;

                      suma:=0;

 for i:=1 to n do    begin

 for j:=1 to m do suma :=suma+v[i,j];  end;















        WRITELN(fout,suma);
                close(fout);
                close(fin);
end.