#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
const long long INF = 1e9;
const double PI = acos(-1);
const int MAX = 100010;
long long fac[MAX], finv[MAX], inv[MAX];
void cmbInit() {
  fac[0] = fac[1] = 1;
  finv[0] = finv[1] = 1;
  inv[1] = 1;
  for (int i = 2; i < MAX; i++) {
    fac[i] = fac[i - 1] * i % MOD;
    inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
    finv[i] = finv[i - 1] * inv[i] % MOD;
  }
}
long long cmb(int n, int k) {
  if (n < k) return 0;
  if (n < 0 || k < 0) return 0;
  return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
int main() {
  ios_base::sync_with_stdio(false);
  int n;
  cin >> n;
  vector<long long> x(n + 1), d(n);
  for (int i = 0; i < n; i++) cin >> x[i + 1];
  for (int i = 0; i < n - 1; i++) d[i + 1] = x[i + 1] - x[i];
  for (int i = 0; i < n - 1; i++)
    d[i + 1] = ((d[i + 1] * (i + 1)) % MOD + d[i]) % MOD;
  long long ans = 0;
  cmbInit();
  for (int i = 1; i < n; i++) {
    long long num = (fac[n - 1] * inv[i]) % MOD;
    ans = (ans + (d[i] * num) % MOD) % MOD;
  }
  cout << ans << endl;
  return 0;
}
