program flip;
type matrice=array[1..100,1..100]of integer;
var i,j,k,m,n,minus,plus:integer;
    a:matrice;
    f,g:textfile;
begin
assign(f,'fisier.in');
reset(f);
read(f,m);
read(f,n);
for i := 1 to m do
  begin
    readln(f);
    for j := 1 to n do
      read(f,a[i,j]);
  end;
close(f);
for i := 1 to m do
  for j := 1 to n do
    if a[i,j]<0 then
      begin
      for k :=1 to m do
        if a[k,j]<0 then
          minus:=minus+a[k,j]*-1
        else
          plus:=plus+a[k,j];
        if minus>plus then
          for k := 1 to m do
            a[k,j]:=a[k,j]*-1;
      minus:=0;plus:=0;
      for k := 1 to n do
        if a[i,k]<0 then
          minus:=minus+a[i,k]*-1
        else
          plus:=plus+a[i,k];
        if minus>plus then
          for k := 1 to n do
            a[i,k]:=a[i,k]*-1;
      end;
k:=0;
for i := 1 to m do
  for j := 1 to n do
  k:=k+a[i,j];
assign(g,'fisier.out');
rewrite(g);
write(g,k);
close(g)
end.