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(*
* Solution to Project Euler problem 25
* Copyright (c) Project Nayuki. All rights reserved.
*
* https://www.nayuki.io/page/project-euler-solutions
* https://github.com/nayuki/Project-Euler-solutions
*)
(*
* Because the target number is relatively small, we simply compute each Fibonacci number starting
* from the beginning until we encounter one with exactly 1000 digits. The Fibonacci sequence grows
* exponentially with a base of about 1.618, so the numbers in base 10 will lengthen by one digit
* after every log10(1.618) ~= 4.78 steps on average. This means the answer is at index around 4780.
*)
digits = 1000;
i = 0;
While[Fibonacci[i] < 10^(digits-1), i++]
i