program dvjdsj;
 var
  f:text;
  n,m,i,j:byte;
  t:array[1..16,1..16] of longint;
  s,st,st2:longint;
 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,t[i,j]);
    readln(f);
   end;
   close(f);
   for i:=1 to n do
    begin
     s:=0;
     for j:=1 to m do
     s:=s +t[i,j];
     if s<0 then
      for j:=1 to m do
      t[i,j]:=-t[i,j];
    end;
     for i:=1 to n do
    for j:=1 to m do
     st:=st+t[i,j];
    for j:=1 to m do
     begin
     s:=0;
     for i:=1 to n do
      s:=s+t[i,j];
     if s<0 then
     for i:=1 to n do
     t[i,j]:=-t[i,j];
     end;
   for i:=1 to n do
    for j:=1 to m do
     st2:=st2+t[i,j];
    if st<st2 then st:=st2;
   assign(f,'flip.out');
   rewrite(f);
   write(f,st);
   close(f);
   end.