MOD=10**9+7

def matmul(A,B,mod): # A,B: 行列
    res = [[0]*len(B[0]) for _ in [None]*len(A)]
    for i, resi in enumerate(res):
        for k, aik in enumerate(A[i]):
            for j,bkj in enumerate(B[k]):
                resi[j] += aik*bkj
                resi[j] %= mod
    return res

def matpow(A,p,M): #A^p mod M
    if p%2:
        return matmul(A, matpow(A,p-1,M), M)
    elif p > 0:
        b = matpow(A,p//2,M)
        return matmul(b,b,M)
    else:
        return [[1 if i == j else 0 for j in range(len(A))] for i in range(len(A))]


a,b,n = [int(i) for i in input().split()]
A = [[0,b],[1,a]]

ans = matpow(A,n,MOD)
print(ans[0][1])