The Fibonacci sequence is defined like this:
\(\varphi_0=0, \varphi_1=1, ..., \varphi_{n}=\varphi_{n-1 }+\varphi_{n-2}\).
Given a number \(n\ge 1\) define \(n\)th Fibonacci number \(\varphi_n\).
Input
A natural number
n is entered.
Imprint
Print the answer to the problem.
Examples
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