import numpy as np


def cumprod(arr, MOD):
    L = len(arr)
    Lsq = int(L**.5 + 1)
    arr = np.resize(arr, Lsq**2).reshape(Lsq, Lsq)
    for n in range(1, Lsq):
        arr[:, n] *= arr[:, n - 1]
        arr[:, n] %= MOD
    for n in range(1, Lsq):
        arr[n] *= arr[n - 1, -1]
        arr[n] %= MOD
    return arr.ravel()[:L]


def make_fact(U, MOD):
    x = np.arange(U, dtype=np.int64)
    x[0] = 1
    fact = cumprod(x, MOD)
    x = np.arange(U, 0, -1, dtype=np.int64)
    x[0] = pow(int(fact[-1]), MOD - 2, MOD)
    fact_inv = cumprod(x, MOD)[::-1]
    return fact, fact_inv


N = int(input())
x = np.array(list(map(int, input().split())))

mod = 10**9 + 7

v = 0
for i in range(N - 1):
    d = x[i + 1:] - x[i]
    v += d.sum() / d.shape[0]
fact, _ = make_fact(N, mod)
print(int(v * fact[-1]) % mod)
