var a:array[1..16,1..16] of longint;
    n,m,i,j,s1,s2:longint;
    f:text;
begin
assign(f,'flip.in');
reset(f);
readln(f,n,m);
for i:=1 to n do
 begin
 for j:=1 to m do
 read(f,a[i,j]);
 readln(f);
 end;
close(f);
assign(f,'flip.out');
rewrite(f);
for j:=1 to m do
 begin
 for i:=1 to n do
 if a[i,j]<0 then s1:=s1+a[i,j]
             else s2:=s2+a[i,j];
 s1:=s1*-1;
 if s2<s1 then for i:=1 to n do
               a[i,j]:=a[i,j]*-1;
 s1:=0;s2:=0;
 end;
for i:=1 to n do
 begin
 for j:=1 to m do
 if a[i,j]<0 then s1:=s1+a[i,j]
             else s2:=s2+a[i,j];
 s1:=s1*-1;
 if s2<s1 then for j:=1 to m do
               a[i,j]:=a[i,j]*-1;
 s1:=0;s2:=0;
 end;
for i:=1 to n do
for j:=1 to m do
s1:=s1+a[i,j];
write(f,s1);
close(f);
end.