program flip;
type xy= array [1..16,1..16] of longint;
var a:xy;
    s,x,s1,i,j,m,n:longint;
    f,g:text;
begin
assign (f,'flip.in');
assign (g,'flip.out');
reset (f);
rewrite (g);
read (f,n,m);
s:=0;
s1:=0;
for i:=1 to n do
for j:=1 to m do
read (f,a[i,j]);
repeat
x:=0;
for i:=1 to n do
begin
s:=0;
for j:=1 to m do
s:=s+a[i,j];
if s<0 then
   begin
   for j:=1 to m do
   a[i,j]:=-a[i,j];
   x:=x+1;
   end;
end;

for i:=1 to m do
begin
s:=0;
for j:=1 to n do
s:=s+a[j,i];
if s<0 then
   begin
   for j:=1 to n do
   a[j,i]:=-a[j,i];
   x:=x+1;
   end;
end;
until x=0;

for i:=1 to n do
for j:=1 to m do
s1:=s1+a[i,j];

write (g,s1);
close (f);
close (g);
end.