#include <bits/stdc++.h>
constexpr int MOD = 1000000007;
constexpr int MAX = 100010;
using ll = long long;
using namespace std;

ll inv(ll x) {
  ll res = 1;
  ll k = MOD - 2;
  ll y = x;
  while (k) {
    if (k & 1) res = (res * y) % MOD;
    y = (y * y) % MOD;
    k /= 2;
  }
  return res;
}

ll f[MAX];
ll h[MAX];
void init() {
  f[0] = 1;
  for (int i = 1; i < MAX; i++)
    f[i] = (f[i - 1] * i) % MOD;
  
  h[0] = 0;
  for (int i = 1; i < MAX; i++)
    h[i] = (h[i - 1] + inv(i)) % MOD;
}

int main() {
  init();
  int n;
  cin >> n;
  vector<ll> x(n);
  for (int i = 0; i < n; i++)
    cin >> x[i];
  
  vector<ll> d(n);
  d[0] = f[n - 1];
  for (int i = 1; i < n - 1; i++) {
    d[i] = f[n - 1] * h[i + 1];
    d[i] %= MOD;
  }
  
  ll total = 0;
  for (int i = 0; i < n - 1; i++) {
    total += d[i] * (x[i+1] - x[i]);
    total %= MOD;
  }
  
  cout << total << endl;
  
  return 0;
}
