# -*- coding: utf-8 -*-

mod = 10**9 +7
N = int(input())
X = list(map(int, input().split()))

factorial=[1]
for i in range(1,N):
    factorial.append(factorial[-1] *i %mod)

ans=0
for i in range(1,N):
    ans = (ans*i + (X[-1]-X[i-1])*factorial[i-1]) %mod

print(ans)