program flip;
type matrice= array[1..17,1..17] of longint;
var a:matrice;
    f:text;
    s:longint;
    m,n,i,j:byte;
begin
assign(f,'flip.in');
reset(f);
read(f,n,m);
for i:=1 to n do

        for j:=1 to m do
               begin
               read(f,a[i,j]);
               s:=s+a[i,j];
               inc(a[i,m+1],a[i,j]);
               inc(a[n+1,j],a[i,j]);
               end;

close(f);

for j:=1 to m do

     if a[n+1,j]<0 then
        begin
        s:=s-2*a[n+1,j];
        for i:=1 to n do
                begin
                a[i,j]:=-a[i,j];
                a[i,m+1]:=a[i,m+1]+a[i,j];
                end;
        end;
for i:=1 to n do
        if a[i,m+1]<0 then
           s:=s-2*a[i,m+1];

assign(f,'flip.out');
rewrite(f);
write(f,s);
close(f);

end.