from fractions import Fraction as Frc
import math

n = int(input())
slime = [int(x) for x in input().split()]

md = 10**9+7
fct = math.factorial(n-1) % md
ans = 0
fr = Frc(1, 1)

for i in range(n-1):
    ans = (ans + fct * (slime[i+1] - slime[i]) % md * fr) % md
    fr += Frc(1, i + 2)
print(ans)
