import numpy as np

#A**n
def mat_pow(A, n, mod):
    size = len(A)
    res = np.eye(size, dtype=np.object)
    while n > 0:
        if n & 1 == 1:
            res = res @ A
            res %= mod
        A = A @ A
        A %= mod
        n = n>>1
    return res

# https://yukicoder.me/problems/no/891
a, b, n = map(int, input().split())
x = np.array([[1], [0]])
mod = 10**9+7

if n <= 1:
    print(x[1-n][0]%mod)
    exit()

A = np.array([[a, b], [1, 0]])
A = mat_pow(A, n-1, mod)
print((A@x)[0][0])