#include<bits/stdc++.h>
#include <array>
using namespace std;
using ULL = unsigned long long;
using UL = unsigned;
using LL = long long;
#define rep(i, n) for(UL i = 0; i < (n); i++)

struct Problem {

	static const ULL M = 1000000007;
	ULL X[100000];
	ULL fac[100001];
	ULL inv[100001];
	ULL dp[100000];

	void Solve() {
		ULL N; cin >> N;
		rep(i, N) cin >> X[i];
		fac[0] = 1;
		for (ULL i = 1; i <= N; i++) fac[i] = fac[i - 1] * i % M;
		inv[1] = 1;
		for (ULL i = 2; i <= N; i++) inv[i] = (M - inv[M % i] * (M / i) % M) % M;
		ULL ans = 0;
		ULL G = 0;
		for (ULL i = 1; i < N; i++) {
			G = (G + inv[i]) % M;
			ans += (X[i] - X[i - 1]) * G;
			ans %= M;
		}
		ans *= fac[N - 1];
		ans %= M;
		cout << ans << endl;
	}

	Problem();
};
int main() {
	unique_ptr<Problem> p(new Problem());
	p->Solve();
	return 0;
}
Problem::Problem() {
	cout << fixed << setprecision(10);
}
