Since the editorial is in japenese. I didn't understand the logic of Task E. Please help
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Since the editorial is in japenese. I didn't understand the logic of Task E. Please help
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We shall consider each $$$A_i$$$ and count number of $$$j > i$$$ such that $$$A_i$$$ and $$$A_j$$$ satisfy the condition. Then the requirement is $$$j - i = A_i + A_j$$$, which can be rewritten as $$$j - A_j = i + A_i$$$. So basically, we need to count the number of $$$j$$$'s for which $$$j-A_j$$$ matches a given value. We can precalculate this value for all indices, store in a map, and query it every time to add to the final answer. Be careful to reduce the count of $$$i - A_i$$$ while moving to the next one. My submission