Jzzhu and Sequences

Description:

Input:

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:

Output a single integer representing f_n modulo 1000000007 (10⁹ + 7).

Sample Input:

2 3
3

Sample Output:

1

Sample Input:

0 -1
2

Sample Output:

1000000006

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).