Fibonacci Number

Given a non-negative integer ( n ), compute the ( n )th Fibonacci number. The Fibonacci sequence is defined as follows: [ F(0)=0,\quad F(1)=1, \quad \text{and} \quad F(n)=F(n-1)+F(n-2) \quad \text{for } n \ge 2. ] Your task is to read an integer from standard input and print the corresponding Fibonacci number to standard output.

inputFormat

The input consists of a single line containing one non-negative integer ( n ) (with ( 0 \le n \le 50 )).

outputFormat

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

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