var a:array[1..16,1..16] of longint;
    f,g:text;
    i,j,m,n:byte;
    s,sc,sl:longint;
begin
assign(f,'flip.in'); reset(f);
assign(g,'flip.out'); rewrite(g);
read(f,n,m); readln(f);
for i:=1 to n do begin
  for j:=1 to m do read(f,a[i,j]);
  readln(f);
end;

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

for i:=1 to m do begin
  sc:=0;
  for j:=1 to n do sc:=sc+a[j,i];
  if sc<0 then for j:=1 to n do a[j,i]:=-a[j,i];
end;
s:=0;
for i:=1 to n do for j:=1 to m do s:=s+a[i,j];
write(g,s);
close(g);
end.