a, b, n = map(int, input().split())
mod = int(1e9)+7
vec = [0, 1]
mat = [[1, 0], [0, 1]]
bas = [[0, 1], [b, a]]
while n != 0:
    t = [[0, 0], [0, 0]]
    if n % 2 == 1:
        for i in range(2):
            for j in range(2):
                for k in range(2):
                    t[i][j] += mat[i][k] * bas[k][j]
                    t[i][j] %= mod
        for i in range(2):
            for j in range(2):
                mat[i][j] = t[i][j]
    for i in range(2):
        for j in range(2):
            t[i][j] = 0
            for k in range(2):
                t[i][j] += bas[i][k] * bas[k][j]
                t[i][j] %= mod
    for i in range(2):
        for j in range(2):
            bas[i][j] = t[i][j]
    n //= 2
print((mat[0][0] * vec[0] + mat[0][1] * vec[1]) % mod)