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Fenwick Prefix Sum Trace API

Rehearse point additions and half-open prefix/range sum queries.

Rehearse point additions and half-open prefix/range sum queries. 1..4096 initial integer values and at most 4096 operations, each supplied value/delta within±1e9, plus shared input limits. Point additions and half-open ranges[start,end), including empty ranges; prefix end may be zero. Public indices are zero-based; tree includes zero dummy cell. BigInt internal sums; no storage changes. Integer result fields use numbers through absolute999999999999 and exact decimal strings beyond that, so shared numerical display rounding cannot change integer results. Uses supplied non-sensitive data only. No live account access, automatic changes or certification. Calculation profile 1.0.0; approximate non-integer numeric outputs use twelve significant digits; representable safe integer numbers and declared decimal-string integers are preserved.

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