Fibonacci Number

The Fibonacci sequence is defined recursively as follows:

\(F(0) = 0,\) \(F(1) = 1,\) and for all \(n \ge 2\), \(F(n) = F(n-1) + F(n-2)\).

Your task is to compute the \(n\)th Fibonacci number using an efficient iterative approach. Please note that the input will be a single non-negative integer and you should output the corresponding Fibonacci number.

inputFormat

The input consists of a single line containing a non-negative integer (n).

outputFormat

Output the (n)th Fibonacci number.## sample

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