CF450B.Jzzhu and Sequences

Jzzhu has invented a kind of sequences, they meet the following property:

You are given $x$ and $y$ , please calculate $f_{n}$ modulo $1000000007$ $(10^{9}+7)$ .

The first line contains two integers $x$ and $y$ $(|x|,|y|<=10^{9})$ . The second line contains a single integer $n$ $(1<=n<=2·10^{9})$ .

Output a single integer representing $f_{n}$ modulo $1000000007$ $(10^{9}+7)$ .

In the first sample, $f_{2}=f_{1}+f_{3}$ , $3=2+f_{3}$ , $f_{3}=1$ .

In the second sample, $f_{2}=-1$ ; $-1$ modulo $(10^{9}+7)$ equals $(10^{9}+6)$ .