var f,g:text;
    n,m,i,j:byte;
    a:array[0..17,0..17]of longint;
    s,p,k:longint;

begin
assign(f,'flip.in');
assign(g,'flip.out');
reset(f);
rewrite(g);
read(f,n);
read(f,m);
for i:=1 to n do
for j:=1 to m do
read(f,a[i,j]);
for k:=1 to 10 do
begin
for i:=1 to n do
begin
s:=0;
p:=0;
for j:=1 to m do
begin
if a[i,j]>=0 then s:=s+a[i,j]
else p:=p+a[i,j]*-1;
end;
if p>s then
begin
for j:=1 to m do
a[i,j]:=a[i,j]*-1;
end;
end;
for j:=1 to m do
begin
s:=0;
p:=0;
for i:=1 to n do
begin
if a[i,j]>=0 then s:=s+a[i,j]
else p:=p+a[i,j]*-1;
end;
if p>s then
begin
for i:=1 to n do
a[i,j]:=a[i,j]*-1;
end;
end;
end;
s:=0;
for i:=1 to n do
for j:=1 to m do
s:=s+a[i,j];
write(g,s);
close(f);
close(g);
end.