Sum of Fibonacci Numbers

Given a positive integer N, compute the sum of the Fibonacci numbers from \(F(0)\) to \(F(N)\). 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\ge2. ]

If the input N is negative, the output should be 0.

Example:

Input: 5
Output: 12
Explanation: The Fibonacci numbers from F(0) to F(5) are: 0, 1, 1, 2, 3, 5. Their sum is 0+1+1+2+3+5=12.

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inputFormat

The input consists of a single integer N provided via standard input.

outputFormat

Output a single integer: the sum of the Fibonacci numbers from \(F(0)\) through \(F(N)\). If N is negative, output 0.

## sample

5

12