mod = 10 ** 9 + 7
def prod(x1, y1, x2, y2, b):
    return (x1 * x2 + b * y1 * y2)%mod, (x1 * y2 + x2 * y1)%mod

def f(x, y, n, a, b):
    if n == 1:
        return a, 1
    if n % 2:
        nx, ny = f(x, y, n//2, a, b)
        nx, ny = prod(nx, ny, nx, ny, b)
        return prod(nx, ny, a, 1, b)
    else:
        nx, ny = f(x, y, n//2, a, b)
        return prod(nx, ny, nx, ny, b)
        
a, b = map(int, input().split())
n = int(input())
if n == 0:
    print(2)
    exit()

print(f(a, 1, n, a, b)[0]*2%mod)