program razvis;
var a:array [1..100,1..100] of longint;
 f,g:text;
 m,n,p,ne,s:longint;
 i,j,q:integer;
begin
assign (f,'flip.in');
reset (f);
assign (g,'flip.out');
rewrite (g);
readln (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
for j:=1 to m do
if a[i,j]>0 then p:=p+a[i,j]
            else ne:=ne+a[i,j];
if ne*(-1)>p then for q:=1 to n do  a[j,q]:=a[j,q]*(-1);
ne:=0;
p:=0;
end;

for i:=1 to n do begin
for j:=1 to m do
if a[j,i]>0 then p:=p+a[j,i]
            else ne:=ne+a[j,i];
if ne*(-1)>p then for q:=1 to n do  a[q,i]:=a[q,i]*(-1);
ne:=0;
p:=0;
end;
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.