program flip;
var f, g:text;
    n, m, i, j, ii, s, sch: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]);
    sch:=1;
    while sch=1 do
      begin
        sch:=0;
        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
                begin
                  for ii:=1 to m do
                    a[i,ii]:=-a[i,ii];
                  sch:=1;
                end;
              s:=0;
              for ii:=1 to n do
                s:=s+a[ii,j];
              if s<0 then
                begin
                  for ii:=1 to n do
                    a[ii,j]:=-a[ii,j];
                  sch:=1;
                end;
            end;
      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.