3) Random Sampling: Let M be the maximum length in S. Let m, 0 ≤ m ≤ M -τ , be the largest index from which a subsequence will be picked. This is another hyperparameter and we call it the maximum offset. Sample an integer k , where m ≤ k ≤ M -τ -m, select a sequence s from S, and sample a subsequence s[k ..k + τ ] padding the necessary number of tokens. Repeat until subsequences are sampled.