#include <bits/stdc++.h>
#pragma once
using namespace std;
#define repd(i,a,b) for (int i=(a);i<(b);i++)
#define rep(i,n) repd(i,0,n)
typedef long long ll;
typedef long double lb;
#define int long long
#define double long double
#define endn "\n"
typedef pair<int,int> P;
const int MOD = 1000000007;
const ll INF = 1e16;
const double EPS = 1e-10;
const double PI = 3.141592653589793;
template<class T> inline bool chmin(T& a, T b){if(a>b){a = b;return 1;}return 0;}
template<class T> inline bool chmax(T& a, T b){if(a<b){a = b;return 1;}return 0;}
const pair<int,int> fd[] = {make_pair(1,0),make_pair(-1,0),make_pair(0,1),make_pair(0,-1)}; 


////////////////////////////////////////////////////////////////////
///////////////////////___modpow___////////////////////
ll modpow(ll a,  ll n, const ll &MOD = MOD){
  ll ret = n == 0 ? 1 : modpow(a, n/2, MOD);
  (ret *= ret) %= MOD;
  if(n%2)((ret *= a) %= MOD);
  return ret;
}
///////////////////////___modinv___////////////////////
ll modinv(ll d, const ll &MOD = MOD){
  return modpow(d, MOD-2, MOD);
}
////////////////////////////////////////////////////////////////////

int n, x[110000];
signed main(){
  cin>>n;rep(i,n)cin>>x[i];
  int ans = 0, a = 1, f;
  repd(i,2,n)a = (a*i)%MOD;
  f = a;
  rep(i,n-1){
    int l = x[i+1] - x[i], t = a*l%MOD;
    ans = (ans + t)%MOD;
    a = (a + f*modinv((i+2)*(i+1)%MOD))%MOD;
  }
  cout << ans << endl;
}
