演習: フィボナッチ

The Fibonacci sequence begins with [0,1]. For n>1, the n’th Fibonacci number is calculated recursively as the sum of the n-1’th and n-2’th Fibonacci numbers.

n 番目のフィボナッチ数を計算する関数 fib(n) を記述します。この関数はいつパニックするでしょうか。

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