type matrice=array[1..16,1..16]of longint;
var f,g:text;
    a:matrice;
    m,n,i,j:byte;
    s1:longint;

function suma (p,k:byte):longint;
var s:longint;
    h:byte;
begin
s:=0;
 if k=1 then begin
           for h:=1 to m do s:=s+a[p,h]; end
        else begin
           for h:=1 to n do s:=s+a[h,p];end;
suma:=s;
end;

procedure modific(p,k:byte);
var H:byte;
begin
if k=1 then begin
         for h:=1 to m do a[p,i]:=a[p,i]*(-1);end
       else begin
         for h:=1 to n do a[h,p]:=a[h,p]*(-1);end;
end;

procedure rezolv(var a:matrice);
begin
for i:=1 to m do
  if suma(i,0)<0 then modific(i,0);
for i:=1 to n do
  if suma(i,1)<0 then modific(i,1);
end;


begin
assign(f,'flip.in');reset(f);
assign(g,'flip.out');rewrite(g);
read(f,n);
read(f,m);
for i:=1 to n do begin
 for j:=1 to m do
  read(f,a[i,j]);
  readln(f);
  end;
rezolv(a);
s1:=0;
{writeln('---------');}
for i:=1 to n do {begin}
 for j:=1 to m do {begin}
   s1:=s1+a[i,j];
{   write(a[i,j]:3);end;
   writeln;end;}
{writeln('---------');}
write(g,s1);
close(g);
end.