Fibonacci Sum

You are given an integer (n) and you are required to compute the sum of the first (n) numbers in the Fibonacci sequence. The Fibonacci sequence is defined as follows: (F(0)=0), (F(1)=1), and for (n \geq 2), (F(n)= F(n-1)+F(n-2)). If (n) is zero or negative, the result should be zero.

inputFormat

Input is read from stdin. It consists of a single integer (n) ((-10^9 \le n \le 10^9)) which represents the number of Fibonacci numbers to sum.

outputFormat

Output to stdout a single integer, which is the sum of the first (n) Fibonacci numbers. If (n) is less than or equal to 0, output 0.## sample

5

7