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