def mt(A, B):
    C = [[0] * 2 for _ in range(2)]
    for i in range(2):
        for j in range(2):
            tmp = 0
            for k in range(2):
                tmp += A[i][k] * B[k][j]
                tmp %= MOD
            C[i][j] = tmp
    return C

MOD = 10 ** 9 + 7
a, b, n = map(int, input().split())
A = [[a, b], [1, 0]]
X = [[1, 0], [0, 1]]
n -= 1
while n:
    if n & 1:
        X = mt(A, X)
    A = mt(A, A)
    n >>= 1
print(X[0][0])