a,b,n = map(int,input().split())
mod = 10**9+7

def calc(x,y):
    ans = [[0]*2 for i in range(2)]
    for i in range(2):
        for j in range(2):
            for k in range(2):
                ans[i][j] += x[i][k]*y[k][j]
                ans[i][j] %= mod

    return ans

if n <= 1:
    print(n)
    exit()
A = [[a,b],[1,0]]
base = [[1,0],[0,1]]
n -= 1
while n:
    if n&1:
        base = calc(A,base)
    A = calc(A,A)
    n //= 2

print(base[0][0])