#include <bits/stdc++.h>
using namespace std;
int main() {
  long long int n, tmp, di = 1000000007, ans;
  vector<long long int> v, p;
  cin >> n;
  v.resize(n + 1);
  p.resize(2020);
  for (int i = 1; i <= n; i++) cin >> v[i];
  p[0] = 1;
  p[1] = 1;
  for (int i = 2; i < 2020; i++) {
    p[i] = p[i - 1] * i;
    p[i] = p[i] % di;
  }
  for (int i = 1; i < n; i++) {
    for (int j = i + 1; j < n + 1; j++) {
      if (i == 1 && j == 2) {
        tmp = p[n - 1];
      } else {
        tmp = p[j - i - 1];
        tmp *= p[n - 1] / p[j - i + 1];
        tmp = tmp % di;
      }
      tmp *= v[j] - v[i];
      tmp = tmp % di;
      ans += tmp;
      ans = ans % di;
    }
  }
  cout << ans << endl;
}
