Language: English Day: 1 a 0 < a 1 < a 2 < · · · n ≥ 1 a n < a 0 + a 1 + · · · + a n n ≤ a n+1 . n ≥ 2 n × n n 2 n k n k × k k 2 ABCD ∠ABC = ∠CDA = 90 ◦ H A BD S T AB AD H SCT ∠CHS − ∠CSB = 90 ◦ , ∠T HC − ∠DT C = 90 ◦ . BD T SH Language: English Day: 2 P Q BC ABC ∠P AB = ∠BCA ∠CAQ = ∠ABC M N AP AQ P AM Q AN BM CN ABC n 1 n 99 + 1 2 100 1 n n √ n √ n c √ n c