#include <iostream>
#include <vector>
using namespace std;

#define readv(v) for(auto& a : v) cin >> a;

using ll = long long int;
using vi = vector<ll>;
using vvi = vector<vi>;

const ll MOD = 1e9+7;

ll power(ll b, ll e){
  if (e == 1) return b;
  if (e % 2 == 0) return power((b*b)%MOD, e/2);
  return (b * power(b, e-1)) % MOD;
}

ll inverse(int i) {
  return power(i, MOD-2);
}

int main(){
  int N; cin >> N;
  vi x(N); readv(x);

  ll fact = 1; // (N-1)!
  for (int i = 2; i < N; i++) fact = (fact * i) % MOD;

  vi cum_sum(N, 0); // cum_sum[i] = /sum_{j=1}^{i} 1/j * (N-1)!
  for (int i = 1; i < N; i++) cum_sum[i] = (cum_sum[i-1] + fact * inverse(i)) % MOD;

  ll total = 0;
  for (int i = 0; i < N-1; i++) total = (total + ((x[i+1] - x[i]) * cum_sum[i+1]) % MOD) % MOD;

  cout << total << endl;
}
