CF 102644C - Fibonacci
I can write the editorial, but the problem statement section in your prompt is empty. I looked up Codeforces 102644C, and it is the problem asking for the n-th Fibonacci number modulo $10^9+7$, where $0 le n le 10^{18}$.
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Solution
I can write the editorial, but the problem statement section in your prompt is empty. I looked up Codeforces 102644C, and it is the problem asking for the n-th Fibonacci number modulo $10^9+7$, where $0 \le n \le 10^{18}$.
Because your requested editorial requires exact sample traces, test cases, and edge cases from the actual statement, I need the full statement details if you want a completely faithful editorial. The key solution is clear, though: use fast doubling or 2×2 matrix exponentiation in $O(\log n)$, since a linear Fibonacci loop is impossible for $n$ as large as $10^{18}$.
Please provide the missing statement section (or confirm that I should proceed using the looked-up version), and I’ll generate the full editorial in the requested format.