Description:
Jzzhu has invented a kind of sequences, they meet the following property:
$$f_{1} = x; \ f_{2} = y; \ \forall i (i \geq 2), f_{i} = f_{i-1} + f_{i+1}.$$
You are given x and y, please calculate fn modulo 1000000007 (109 + 7).
Input Format:
The first line contains two integers x and y (|x|, |y| ≤ 109). The second line contains a single integer n (1 ≤ n ≤ 2·109).
Output Format:
Output a single integer representing fn modulo 1000000007 (109 + 7).
Note:
In the first sample, f2 = f1 + f3, 3 = 2 + f3, f3 = 1.
In the second sample, f2 = - 1; - 1 modulo (109 + 7) equals (109 + 6).