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

mod = 10 ** 9 + 7

c = [1]
for i in range(1,N-1):
    c.append(c[i-1]+(1/(i+1)))

ans = 0
for i in range(N-1):
    ans += (c[i] * (x[i+1] - x[i])) % mod
    ans %= mod
    
for i in range(1,N):
    ans *= i
    ans %= mod

print(round(ans))