uses crt;
type matrice=array[1..1000,1..1000]of longint;
var a:matrice;
    f,g:text;
    n,m,i,j,l,s,h,k:longint;
begin
clrscr;
assign(f,'flip.in');
reset(f);
read(f,n,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:=0;
   for h:=1 to m do s:=s+a[i,h];
   if s<0 then for h:=1 to m do a[i,h]:=a[i,h]*(-1);
   for j:=1 to m do
       begin
       if a[i,j]<0 then
              begin
              s:=0;
              for l:=1 to n do s:=s+a[l,j];
              if s<0 then for k:=1 to l do a[k,j]:=a[k,j]*(-1);
              end;
       end;
   end;
s:=0;
for i:=1 to n do
  for j:=1 to m do s:=s+a[i,j];
assign(g,'flip.out');
rewrite(g);
write(g,s);
close(g);
end.