#include "bits/stdc++.h"
#pragma warning(disable:4996)
using namespace std;
#define int long long
#define rep(i,n) for(int i=0;i<n;i++)
const int mod = 1000000007;
const long long inf = 1ll << 61;
typedef pair<int, int> P;
typedef pair<int, P>PP;
int x[100006];
int kj[100006];
int c[100006];

int modpow(int a, int x, int mod) {
	int res = 1;
	while (x) {
		if (x & 1)res = res*a%mod;
		a = a*a%mod;
		x >>= 1;
	}
	return res;
}

signed main() {
	int n; cin >> n;
	rep(i, n)cin >> x[i];
	kj[0] = 1;
	rep(i, n + 1)kj[i + 1] = (kj[i] * (i + 1)) % mod;
	c[0] = kj[n-1];
	rep(i, n - 2) {
		c[i + 1] = c[i] + kj[n - 1] * modpow((i + 2), mod - 2, mod) % mod;
		c[i + 1] %= mod;
	}
	int ans = 0;
	rep(i, n - 1) {
		ans += c[i] * (x[i + 1] - x[i]) % mod;
		ans %= mod;
	}
	cout << ans << endl;
}
