var f1, f2:text;
a:array[1..100, 1..100] of integer;
 s1,s,i,j,n,m:integer;
begin
assign(f1, 'flip.in');
reset(f1);
readln(f1, n,m);
writeln;
for i:=1 to n do
for j:=1 to m do 
read(f1, a[i,j]);
writeln;

i:=1;
for j:=1 to n do
begin

s:=s+a[i,j];
s1:=s1+a[i,j]*(-1);
end;
if s<s1 then 
for j:=1 to n do a[i,j]:=a[i,j]*(-1);


 
assign(f2, 'flip.out');
rewrite(f2);
writeln(f2, s);
close(f2);

end.