m=10**9+7
A,B=map(int,input().split())
N=int(input())

def f(a,b,c,n):
    x,y=1,0
    while n:
        if n&1: x,y=(x*a+y*c*b)%m,(x*c+y*a)%m
        a,c=(a*a+c*c*b)%m,a*c*2%m
        n=n>>1
    return x

print((f(A,B,1,N)+f(A,B,-1,N))%m)