n = int(input())
xl = list(map(int,input().split()))

bl = []

for i in range(n-1):
    bl.append(xl[i+1] - xl[i])

import itertools
bl_ac = list(itertools.accumulate(bl))

MOD = 10**9 + 7
N = 10**5

fact = [1]*(N+1)
rfact = [1]*(N+1)
r = 1
for i in range(1, N+1):
  fact[i] = r = r * i % MOD
rfact[N] = r = pow(fact[N], MOD-2, MOD)
for i in range(N, 0, -1):
  rfact[i-1] = r = r * i % MOD

# nPk (mod MOD) を求める
def perm(n, k):
  return fact[n] * rfact[n-k] % MOD

# nCk (mod MOD) を求める
def comb(n, k):
  return fact[n] * rfact[k] * rfact[n-k] % MOD

ans = 0
p = 1
c = 1
for i in range(n-1):
    ans += bl[i] * perm(n-1, n-2-i) * c
    ans %= MOD
    c *= i + 2
    c += p
    c %= MOD
    p *= i + 2
    p %= MOD

print(ans)