import sys
import math
#import numpy as np

stdin = sys.stdin

ri = lambda: int(rs())
rl = lambda: list(map(int, stdin.readline().split())) # applies to numbers only
rs = lambda: stdin.readline().rstrip()  # ignore trailing spaces

N = ri()
X = rl()
MOD = 10 ** 9 + 7
limit = math.factorial(N-1)
last = X[-1]
X = [last - x for x in X] #最後までの距離
answer = 0
for i in range(1, N):
    answer += X[i-1] * (limit // i)%MOD
    answer %= MOD

print(answer)

