import math
def comb(n, r):
    return math.factorial(n) // (math.factorial(n - r) * math.factorial(r))


MOD = int(1e9+7)
n = int(input())
combs=[comb(n-1,i) for i in range(n-1)]
a = input().split()
ans = 0
for i,j in enumerate(a):
    ans += int(j)*combs[int(i)]
    ans %= MOD
print(ans)