var a:array[1..16,1..16] of longint;
    n,m,i,j:byte;
    f,g:text;
    s,slinie,scoloana:longint;
procedure citire;
begin
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;
end;
procedure parcurgere;
begin
for j:=1 to m do begin
  scoloana:=0;
  for i:=1 to n do scoloana:=scoloana+a[i,j];
  if scoloana<0 then for i:=1 to n do a[i,j]:=-a[i,j];
end;
for i:=1 to n do begin
  slinie:=0;
  for j:=1 to m do slinie:=slinie+a[i,j];
  if slinie<0 then for j:=1 to m do a[i,j]:=-a[i,j];
end;
for i:=1 to n do begin
  for j:=1 to m do s:=s+a[i,j];
end;
end;
procedure scriere;
begin
write(g,s);
close(g);
end;
begin
assign(f,'flip.in'); reset(f);
assign(g,'flip.out'); rewrite(g);
citire;
parcurgere;
scriere;
end.