Tail/arc-compression with threshold N/4. The previous 31-set already lies entirely in the upper N/4 tail. A direct tail-preserving 1→2 exchange works immediately: remove 1185 and insert 1435,1440. This gives the size-32 witness above, all residues >N/4.
Yongxi (Aaron) Lin · 2026-08-09 18:27:09 UTC