'''
研究室PCでの解答
'''
import math
#import numpy as np
import queue
import bisect
from collections import deque,defaultdict
import heapq as hpq
from sys import stdin,setrecursionlimit
#from scipy.sparse.csgraph import dijkstra
#from scipy.sparse import csr_matrix
ipt = stdin.readline
setrecursionlimit(10**7)
mod = 10**9+7 #998244353
dir = [(-1,0),(1,0),(0,-1),(0,1)]
alp = "abcdefghijklmnopqrstuvwxyz"


def main():
    n = int(ipt())
    x = [int(i) for i in ipt().split()]
    d = [x[i+1]-x[i] for i in range(n-1)]
    k = [1]
    for i in range(1,n):
        k.append(k[-1]*i%mod)

    #n!の逆元を求める
    g2 = [1,1]
    inverse = [0,1] #逆元テーブル計算用テーブル
    for i in range(2,n+1):
        inverse.append((-inverse[mod%i]*(mod//i))%mod)
        g2.append((g2[-1]*inverse[-1])%mod)

    ans = 0
    na = 0
    for i in range(1,n):
        na = na*i+k[i-1]
        ans += na*d[i-1]*k[-1]*g2[i]
        ans %= mod

    print(ans)
    return None

if __name__ == '__main__':
    main()
