#include <bits/stdc++.h>
using namespace std;
const int MAX = 510000;
const int MOD = 1000000007;
long long n;
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 rei(long long k) {
  long long ans = 0;
  for (int i = 1; i <= k; i++) {
    ans += finv[i] % MOD;
    ans %= MOD;
  }
  return ans;
}
int main() {
  std::cin >> n;
  vector<long long> x(n);
  COMinit();
  for (int i = 0; i < n; i++) {
    std::cin >> x[i];
  }
  long long sum = 0;
  for (int i = 0; i < n - 1; i++) {
    sum += (x[i + 1] - x[i]) % MOD * rei(i + 1) % MOD;
    sum %= MOD;
  }
  std::cout << fac[n - 1] * sum % MOD << std::endl;
}
