#include <bits/stdc++.h>
using namespace std;
const int MAX = 510000;
const long long int MOD = 1000000007;
long long fac[MAX], finv[MAX], inv[MAX];
void COMinit() {
  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 COM(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;
}
long long FINV(int n) {
  if (n < 0) return 0;
  return finv[n];
}
int main() {
  COMinit();
  long long int n;
  cin >> n;
  long long int a[n];
  for (int i = 0; i < (n); ++i) {
    cin >> a[i];
  }
  long long int ans = 0;
  for (int i = 0; i < (n - 1); ++i) {
    long long int tmp = 0;
    for (int j = i + 1; j < n; ++j) {
      long long int tmp2 = 0;
      if (j == n - 1) {
        tmp2 += inv[j - i] * (a[j] - a[i]) % MOD;
      } else {
        tmp2 += inv[j - i] * inv[j - i + 1] % MOD * (a[j] - a[i]) % MOD;
      }
      tmp2 %= MOD;
      tmp2 = tmp2 * fac[n - 1] % MOD;
      tmp += tmp2;
    }
    ans += tmp;
    ans %= MOD;
  }
  cout << ans << endl;
  return 0;
}
