#include <bits/stdc++.h>
struct Mint {
  static const long long mod = (long long)1e9 + 7;
  long long val;
  Mint() { val = 0; }
  Mint(long long a) {
    val = a;
    verify_value();
  }
  void verify_value() {
    if (val >= mod) val %= mod;
    if (val < 0) val %= mod, val += mod;
  }
  Mint pow(long long p) const {
    Mint cur = Mint(val), ret = 1;
    while (p > 0) {
      if (p & 1) ret *= cur;
      cur *= cur;
      p >>= 1LL;
    }
    return ret;
  }
  Mint inv() const {
    if (val == 0) std::cerr << "WARNING: inv() is called with 0." << std::endl;
    return pow(mod - 2);
  }
  Mint operator+() const { return *this; }
  Mint operator-() const { return Mint(mod - val); }
  Mint operator+=(const Mint &a) {
    val += a.val;
    if (val >= mod) val -= mod;
    return Mint(val);
  }
  Mint operator*=(const Mint &a) {
    val *= a.val;
    if (val >= mod) val %= mod;
    return Mint(val);
  }
  Mint operator-=(const Mint &a) { return *this += -a; }
  Mint operator/=(const Mint &a) { return *this *= a.inv(); }
  Mint operator++() { return *this += Mint(1); }
  Mint operator--() { return *this -= Mint(1); }
  Mint operator++(int) {
    Mint ret = *this;
    ++(*this);
    return ret;
  }
  Mint operator--(int) {
    Mint ret = *this;
    --(*this);
    return ret;
  }
  operator long long() const { return val; }
};
Mint operator+(const Mint &a, const Mint &b) {
  long long ret = a.val + b.val;
  if (ret >= Mint::mod) ret -= Mint::mod;
  return Mint(ret);
}
Mint operator*(const Mint &a, const Mint &b) {
  long long ret = a.val * b.val;
  if (ret >= Mint::mod) ret %= Mint::mod;
  return Mint(ret);
}
Mint operator-(const Mint &a, const Mint &b) { return a + (-b); }
Mint operator/(const Mint &a, const Mint &b) { return a * b.inv(); }
std::ostream &operator<<(std::ostream &out, const Mint &a) {
  return out << a.val;
}
std::istream &operator>>(std::istream &in, Mint &a) {
  in >> a.val;
  a.verify_value();
  return in;
}
Mint pow(Mint a, long long b) { return a.pow(b); }
constexpr int MAX_N = 200003;
std::vector<Mint> fact(MAX_N), inv(MAX_N);
void init_fact() {
  fact[0] = inv[0] = 1;
  for (long long i = 1; i < MAX_N; i++) {
    fact[i] = fact[i - 1] * Mint(i);
    inv[i] = fact[i].inv();
  }
}
Mint C(int a, int b) {
  if (a < 0 || b < 0 || a < b) return 0;
  Mint res = fact[a];
  res *= inv[b];
  res *= inv[a - b];
  return res;
}
Mint P(int a, int b) {
  if (a < 0 || a < b) return 0;
  return fact[a] * inv[a - b];
}
Mint H(int a, int b) {
  if (b == 0) return 1;
  return C(a + b - 1, b);
}
int main() {
  init_fact();
  int n;
  std::cin >> n;
  std::vector<Mint> x(n), d(n + 1);
  for (int i = 0; i < n; i++) std::cin >> x[i];
  Mint ans = 0;
  for (int i = 0; i < n - 1; i++) {
    for (int j = i; j < n - 1; j++) {
      int left = j - i;
      int res = n - 2 - left - (j != n - 2);
      ans += (x[j + 1] - x[i]) * fact[left] * fact[res] *
             H(res + 1, j - i + 1 + (j != n - 2));
    }
  }
  std::cout << ans << std::endl;
  return 0;
}
