Description
In mathematics, the Fibonacci numbers can be defined by the recurrence relation:
For example, if n = 3, the corresponding result will be 3.
Here, we want to find the reverse Fibonacci numbers defined by a similar but different recurrence relation:
For example, if G0 = 1, G1=-1, the reverse Fibonacci sequence will be like: 1,-1,2,-3,5,-8, ....
In this problem, given G0, G1, and n, please calculate Gn.
Input
There will be three integers(G0, G1, and n) separated by white space.
Note: ( -100000 <=G0, G1<= 100000) and (0 <= n <= 30)
Output
The nth number, Gn, in the reverse Fibonacci number.
Note that you need to print "\n" at the end.