There are N slimes standing on a number line. The i-th slime from the left is at position x_i.

It is guaruanteed that 1 \leq x_1 < x_2 < \ldots < x_N \leq 10^{9}.

Niwango will perform N-1 operations. The i-th operation consists of the following procedures:

* Choose an integer k between 1 and N-i (inclusive) with equal probability.
* Move the k-th slime from the left, to the position of the neighboring slime to the right.
* Fuse the two slimes at the same position into one slime.



Find the total distance traveled by the slimes multiplied by (N-1)! (we can show that this value is an integer), modulo (10^{9}+7). If a slime is born by a fuse and that slime moves, we count it as just one slime.

Constraints

* 2 \leq N \leq 10^{5}
* 1 \leq x_1 < x_2 < \ldots < x_N \leq 10^{9}
* x_i is an integer.

Input

Input is given from Standard Input in the following format:


N
x_1 x_2 \ldots x_N


Output

Print the answer.

Examples

Input

3
1 2 3


Output

5


Input

12
161735902 211047202 430302156 450968417 628894325 707723857 731963982 822804784 880895728 923078537 971407775 982631932


Output

750927044
n = int(input())
x = list(map(int, input().split()))

MOD = 10 ** 9 + 7

class ModInv:
    def __init__(self, size, MOD):
        self.inv = [0] * (size + 1)
        self.inv[1] = 1
        for i in range(2, size + 1):
            self.inv[i] = (-(MOD // i) * self.inv[MOD%i]) % MOD

inv = ModInv(n, MOD)

#print(inv.inv)

b = 1
for i in range(1, n):
    b = (b * i) % MOD

ans = 0
temp = 0
for i in range(1, n):
    temp += inv.inv[i]
    ans += (x[i] - x[i-1]) * temp
    ans %= MOD

print((ans * b) % MOD)