var a:array[1..16,1..16] of longint;
    n,m,i,j:byte;
    s1,s2,s:int64;
begin
assign(input,'flip.in');reset(input);
assign(output,'flip.out');rewrite(output);
readln(n,m);
s:=0;
for i:=1 to n do begin
 for j:=1 to m-1 do
  read(a[i,j]);
 readln(a[i,m]); end;
for i:=1 to n do begin
 s1:=0;
 s2:=0;
  for j:=1 to m do
    s1:=s1+a[i,j];
    s2:=-s1;
 if s1<s2 then begin
  for j:=1 to m do
   a[i,j]:=a[i,j]*(-1);
 end;
end;
for i:=1 to m do begin
 s1:=0;
 s2:=0;
  for j:=1 to n do
    s1:=s1+a[j,i];
    s2:=-s1;
 if s1<s2 then begin
  for j:=1 to n do
   a[j,i]:=a[j,i]*(-1);
 end;
end;
for i:=1 to n do
 for j:=1 to m do
  s:=s+a[i,j];
write(s);
close(input); close(output);
end.