program cui_ii_pasa8;
var v:array[1..16,1..16] of integer;
    n,m,i,j,k:longint;
    f:text;
    s,sp:longint;

begin

assign(f,'flip.in');
reset(f);
read(f,n);
read(f,m);

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

close(f);

for i:=1 to n do
  begin
    sp:=0;
    for j:=1 to m do
      begin
        sp:=sp+v[i,j];
      end;
    if sp<0 then
      for k:=1 to m do
        v[i,k]:=v[i,k]*(-1);
  end;
for j:=1 to m do
  begin
    sp:=0;
    for i:=1 to n do
      begin
        sp:=sp+v[i,j];
      end;
    if sp<0 then
      for k:=1 to n do
        v[k,j]:=v[k,j]*(-1);
  end;
for i:=1 to n do
  begin
    sp:=0;
    for j:=1 to m do
      begin
        sp:=sp+v[i,j];
      end;
    if sp<0 then
      for k:=1 to m do
        v[i,k]:=v[i,k]*(-1);
  end;

s:=0;
for i:=1 to n do
  for j:=1 to m do
    begin
      s:=s+v[i,j];
    end;

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





                  {
for i:=1 to n do
  begin
    for j:=1 to m do
      begin
        write(v[i,j],' ');
      end;
    writeln;
  end;
writeln;
writeln(s);
readln;




                   }


end.