#include "bits/stdc++.h"
using namespace std;
#define rep(i,n) for(int i=0;i<n;++i)
typedef long long ll;
ll mod = 1e9+7;
ll modpow(ll a, ll b) {
	ll c = 1;
	while (b > 0) {
		if (b & 1) c = a * c%mod; 
    	a = a * a%mod;
    	b >>= 1;
	}
	return c;
}
int main() {
    ll n;
	cin >> n;
	vector<ll> a(n);
	rep(i, n) { cin >> a[i]; }
	//(N-1)!
	ll fac = 1;
	for(int i=1; i<n; i++) fac = fac * i%mod;
	//mod inverse(逆元)
	//fermatの小定理版
	vector<ll> cnt(n);
	for(int i=1; i<n; i++) {
		cnt[i] = fac * modpow(i, mod - 2) % mod;
		cnt[i] = (cnt[i] + cnt[i - 1]) % mod;
	}
    ll ans = 0;
	rep(i, n-1) {
		ans += (a[i + 1] - a[i]) * cnt[i+1];
		ans %= mod;
	}
	cout << ans << endl;
}
