{Jocul FLIP. www.InfoArena.pas}
type MATRICE = array[1..16,1..16] of integer;
var i,j : byte;
    f   : text;
    a:matrice;
    n,m:byte;
    suma:longint;
begin
     Assign(f,'flip.in'); Reset(f);
     Readln(f,n,m);
     suma:= 0;
     for i:=1 to n do
         for j:=1 to m do
             Read(f,A[i,j]);
     for i:=1 to n do
         for j:=1 to m do
             suma:=suma+abs(a[i,j]);
     Close(f);
     assign (f,'flip.out');
     rewrite (f);
     write (f,suma);
     close(f);
end.