program flip;
var f : text;
    t : array[1..16,1..16] of longint;
    n,m,i,j : byte;
    s,p : 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);

    repeat

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

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

    until p = 0;

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

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