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