MOD = 10**9+7

def inverse(n, d):
    return n * pow(d, -1, MOD) % MOD

N = int(input())
X = list(map(int, input().split()))

sumX = sum(X)
ans = sumX%MOD
for x in X:
    ans -= inverse(x, sumX)*(x-1)%MOD
    ans %= MOD

print(ans)