var f,g:text;
    i,j,n,m:byte;
    sp,sm:longint;
    a:array[1..20,1..16]of longint;
begin
assign(f,'flip.in');reset(f);
assign(g,'flip.out');rewrite(g);
read(f,n,m);
for i:=1 to n do
for j:=1 to m do
read(f,a[i,j]);
for i:=1 to n do begin
sp:=0;sm:=0;
for j:=1 to m do
if a[i,j]<0 then
sm:=sm+a[i,j]
else sp:=sp+a[i,j];
if abs(sm)>sp then
for j:=1 to m do
a[i,j]:=a[i,j]*(-1);
end;
for i:=1 to m do begin
sp:=0;sm:=0;
for j:=1 to n do
if a[j,i]<0 then
sm:=sm+a[j,i]
else sp:=sp+a[j,i];
if abs(sm)>sp then
for j:=1 to n do
a[j,i]:=a[j,i]*(-1);
end;
sm:=0;
for i:=1 to n do
for j:=1 to m do
sm:=sm+a[i,j];
write(g,sm);
close(f);
close(g);
end.