345.lean:1:12-1:13: error: typeclass instance problem is stuck, it is often due to metavariables
  OfNat (Sort ?u) 1
345.lean:4:8-4:9: error: typeclass instance problem is stuck, it is often due to metavariables
  OfNat (Sort ?u) 1
345.lean:6:19-6:20: error: typeclass instance problem is stuck, it is often due to metavariables
  OfNat (Sort ?u) 1