import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

import numpy as np

def matrixPow(A, n, N, mod):
	B = np.identity(N, dtype = np.int)
	while n > 0:
		if n & 1 == 1:
			B = (A @ B) % mod
		A = (A @ A) % mod
		n >>= 1
	return B


#処理内容
def main():
	a, b, n = getlist()

	A = np.array([[a, b], [1, 0]])
	mat = matrixPow(A, n, 2, con)

	ans = (mat @ np.array([[1], [0]]))[1, 0]
	print(ans % con)


if __name__ == '__main__':
	main()