In Lightroom Classic, select photos without a flag

The other day I was judging pictures in Lightroom. As usual, most of them were not as good as expected and could be thrown away. Problem: I had only flagged the ones to keep (using 'P'). 

If I had used 'X' for the ones to reject, it would have been easy to actually delete them. 'Ctrl+Backspace' removes all rejected photos. But what to do now? 

 Then I saw the solution: ordering. 

1. In the toolbar below, select ordering on 'Choice' - this is based on the flag you assigned. 
2. Then scroll to the first non-flagged picture. 
3. Shift-select until the end. 
4. Delete.