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