Anti-Subarray Sum

You've been working with subarrays for so long that you're sick of them – subarrays are now banned! Formally, consider a set of *indices* $\{i_1, i_2, \ldots, i_k\}$ such that $1 \leq i_1 \lt i_2 \lt \cdots \lt i_k \leq N$. This set is said to be an *anti-subarray* if $i_k - i_1 \gt k - 1$. In particular, note that an anti-subarray must have length greater than $1$. --- You have an array