var f1, f2:text;
a:array[1..100, 1..100] of integer;
 s3,s4,s1,p,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;

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

s:=s+a[i,j];
s1:=s1+a[i,j]*(-1);
end;


if s<s1 then 
for i:=1 to n do
for j:=1 to m do a[i,j]:=a[i,j]*(-1);
 
 for i:=1 to n do 
 for j:=1 to n do p:=p+a[i,j];
 
assign(f2, 'flip.out');
rewrite(f2);
writeln(f2, p);
close(f2);

end.