#!/usr/bin/env python3

import numpy


M = 10 ** 9 + 7


def mat_mul_mod(x, y, mod=M):
    return x @ y % mod


def mat_pow_mod(x, n, mod=M):
    y = numpy.array([[1, 0], [0, 1]], dtype=numpy.int64)
    while n > 0:
        if n % 2 == 1:
            y = mat_mul_mod(y, x, mod)
        x = mat_mul_mod(x, x, mod)
        n >>= 1
    return y


def solve(a, b, n, mod=M):
    x = numpy.array([[a, b], [1, 0]], dtype=numpy.int64)
    res = mat_pow_mod(x, n)
    z = numpy.array([[1, ], [0, ]], dtype=numpy.int64)
    res = mat_mul_mod(res, z, mod)
    return res[1, 0]


def main():
    a, b, n = (int(z) for z in input().split())
    ans = solve(a, b, n)
    print(ans)


if __name__ == "__main__":
    main()