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

def prod(A, B):
    n = len(A)
    m = len(B)
    l = len(B[0])
    C = [[0]*l for _ in range(n)]
    for i in range(n):
        for j in range(m):
            for k in range(l):
                C[i][k] += A[i][j] * B[j][k]
                C[i][k] %= mod
    return C
def mpow(X, n):
    if n == 0:
         return [[1,0], [0,1]]
    if n%2:
        return prod(X, mpow(X,n-1))
    Y = mpow(X, n//2)
    return prod(Y, Y)
X = [[a,b], [1,a]]
A = [[1],[0]]
L = prod(mpow(X,n),A)
ans = L[0][0]*2%mod
print(ans)