import math
N = int(input())
x = list(map(int,input().split()))

d = [0]*(N-1)
for i in range(N-1):
    d[i] = x[i+1]-x[i]
    d[i] %= 10**9+7


kaijou = 1
for i in range(1,N):
    kaijou *= i%(10**9+7)

kaijou = math.factorial(N-1)%(10**9+7)
ans=0
x=0
k=10**9+5

def pow_r(x, n):
    """
    O(log n)
    """
    x %= (k+2)
    if n == 0:  # exit case
        return 1
    if n % 2 == 0:  # standard case ① n is even
        return pow_r(x ** 2, n // 2)%(k+2)
    else:  # standard case ② n is odd
        return (x * pow_r(x ** 2, (n - 1) // 2))%(k+2)

for i in range(N-1):
    #(i+1)**(10**9+5)を計算してyへ
    y = pow_r(i+1,k) 
    #x+= kaijou//(i+1))%(10**9+7)
    x += (kaijou*y)%(10**9+7)
    ans+= d[i]*x

print(ans%(10**9+7))