import numpy as np

def multiply_matrices(A, B, mod):
    return np.dot(A, B) % mod

def power_matrix(A, n, mod):
    result = np.identity(len(A), dtype=int)
    while n > 0:
        if n % 2 == 1:
            result = multiply_matrices(result, A, mod)
        A = multiply_matrices(A, A, mod)
        n //= 2
    return result

a, b, n = map(int, input().split())
mod = 1000000007
A = np.array([[0, 1], [b, a]])
A_cube = power_matrix(A, n, mod)
print(A_cube[0][1])