a, b, n = [ int(v) for v in input().split() ]

path_mat = [ [a, b], [1, 0] ]
mod = 10**9+7

def mat_mul(inmat1,inmat2,m):
    outmat = [ [ 0 for j in range(m) ] for i in range(m) ]

    for i in range(m):
        for j in range(m):
            for g in range(m):
                outmat[i][j] += inmat1[i][g] * inmat2[g][j]
            outmat[i][j] %= mod
    return outmat


ans_mat = [ [ 1 if i == j else 0 for j in range(2) ] for i in range(2) ]

while n != 0:
    if n % 2 == 1:
        ans_mat = mat_mul(ans_mat,path_mat,2)
    n = n // 2
    path_mat = mat_mul(path_mat,path_mat,2)
    
print(ans_mat[1][0])