#include "bits/stdc++.h"
using namespace std;

long long MOD = 1000000007;
vector<long long> F;

long long Calc(long long A, long long B) {
	if (B == 0) return 1;
	if (B % 2 == 0) {
		long long C = Calc(A, B / 2);
		return (C * C) % MOD;
	}
	return (A * Calc(A, B - 1)) % MOD;
}

void init(long long N) {
	F.resize(N + 1);
	F[0] = F[1] = 1;
	for (long long i = 2; i <= N; i++) {
		F[i] = (F[i - 1] * i) % MOD;
	}
	return;
}

int main() {
	long long N, ANS = 0, Cur = 0;
	vector<long long> X;
	cin >> N;
	X.resize(N);
	init(N);
	for (int i = 0; i < N; i++) cin >> X[i];
	for (int i = 1; i < N; i++) {
		long long COUNT = (F[N - 1] * Calc(i, MOD - 2)) % MOD;
		Cur = (Cur + COUNT) % MOD;
		ANS = (ANS + Cur * (X[i] - X[i - 1])) % MOD;
	}
	cout << ANS << endl;
}