Fig. 6: AlphaGeometry proof length versus the average score of IMO participants on different problems.
From: Solving olympiad geometry without human demonstrations

Among the solved problems, 2000 P6, 2015 P3 and 2019 P6 are the hardest for IMO participants. They also require the longest proofs from AlphaGeometry. For easier problems, however, there is little correlation between AlphaGeometry proof length and human score.