Challenge: Maximum Pairwise Product

Problem

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Maximum Pairwise Product Problem

Find the maximum product of two distinct numbers in a sequence of non-negative integers.

Input: A sequence of $n$ non-negative integers.

Output: The maximum value that can be obtained by multiplying two different elements from the sequence.

Given a sequence of non-negative integers $a_{1},...,a_{n}$, compute

$$max_{1 \leqslant i \neq j \leqslant n} a_{i} \cdot a_{j}.$$ ...