program flip;
var f,g:text;
    a:array[1..16,1..16] of longint;
    x,i,j,n,m,s:longint;
    vcp,vcn,vlp,vln:array[1..16] of longint;
begin
assign(f,'flip.in');
reset(f);
readln(f,n,m);
for i:=1 to n do
  begin
    vlp[i]:=0;
    vln[i]:=0;
  end;
for j:=1 to m do
  begin
    vcp[i]:=0;
    vcn[i]:=0;
  end;
for i:=1 to n do
   begin
  for j:=1 to m do
    begin
      read(f,x);
      a[i,j]:=x;
      if x>=0 then
         begin
           vlp[i]:=vlp[i]+x;
           vcp[j]:=vcp[j]+x;
         end
             else
         begin
           vln[i]:=vln[i]+abs(x);
           vcn[j]:=vcn[j]+abs(x);
         end;
    end;
  end;
close(f);
for i:=1 to n do
   if vlp[i]<vln[i] then for j:=1 to m do a[i,j]:=0-a[i,j];
for j:=1 to m do
   if vcp[j]<vcn[j] then for i:=1 to n do a[i,j]:=0-a[i,j];
s:=0;
for i:=1 to n do
  for j:=1 to m do
    s:=s+a[i,j];
assign(g,'flip.out');
rewrite(g);
writeln(g,s);
close(g);
end.