Program flip2 ;
var a,a1: array[1..16,1..16] of longint;
      n,m,i,j,s,k,sm : longint;
      f1,f2:text;
      cont: boolean;
Procedure citire;
Begin
     assign(f1, 'flip.in');
     assign(f2, 'flip.out');
     reset(f1);
     readln(f1,n,m);
     for i:=1 to n do
         for j:=1 to m do
             read(f1,a[i,j]);
     close(f1);
end;

Begin
     citire;
     repeat
                cont:=true;
                for i:=1 to n do
                    Begin
                         sm:=0;
                         for j:=1 to m do
                             sm:=sm+a[i,j];
                         if sm<0 then Begin
                            cont:=false;
                            for j:=1 to m do
                                a[i,j]:=a[i,j]*-1;
                                      end;
                    end;
                for i:=1 to m do
                    Begin
                         sm:=0;
                         for j:=1 to n do
                             sm:=sm+a[j,i];
                         if sm<0 then Begin
                            cont:=false;
                            for j:=1 to n do
                                a[j,i]:=a[j,i]*-1;
                                       end;
                    end;
     until (k>1) and cont;
     for i:=1 to n do
         for j:=1 to m do
             s:=s+ a[i,j];
     rewrite(f2);
     writeln(f2,s);
     close(f2);
end.