mod = 10**9 + 7

def matmul(A, B):
    Ah, Bh, Bw = len(A), len(B), len(B[0])
    C = [[0 for _ in range(Bw)] for _ in range(Ah)]
    for i in range(Ah):
        for j in range(Bw):
            for k in range(Bh):
                C[i][j] += A[i][k] * B[k][j] % mod
                C[i][j] %= mod
    return C

# Mのk乗を効率的に計算する
def doubling(M, k):
    k -= 1
    Mc = M.copy()
    while k > 0:
        if k & 1 == 1:
            Mc = matmul(Mc, M)
        M = matmul(M, M) # Mの(2のi乗)の乗 を計算する
        k >>= 1
    return Mc

a, b, n = map(int, input().split())
if n == 0:
    print(0)
    exit()
elif n == 1:
    print(1)
    exit()
X = [[a, b], [1, 0]]
XX = doubling(X, n - 1)
F = [[1], [0]]
T = matmul(XX, F)
print(T[0][0])