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
import sys
from math import factorial

rl = sys.stdin.readline


def mod_div(x, y, mod=10 ** 9 + 7):
    return x * pow(y, mod - 2, mod) % mod


def solve():
    N = int(rl())
    x = list(map(int, rl().split()))
    MOD = 10 ** 9 + 7
    
    acc = [0] * N
    k = factorial(N - 1)
    for i in range(1, N):
        acc[i] = (acc[i - 1] + k) % MOD
        k = k * mod_div(i, i + 1) % MOD
    
    ans = 0
    for i in range(N - 1):
        ans = (ans + (x[i + 1] - x[i]) * acc[i + 1]) % MOD
    print(ans)


if __name__ == '__main__':
    solve()
