#include <bits/stdc++.h>
using namespace std;
template <class T>
void chmin(T& a, const T& b) {
  if (a > b) a = b;
}
template <class T>
void chmax(T& a, const T& b) {
  if (a < b) a = b;
}
template <class T>
using MaxHeap = priority_queue<T>;
template <class T>
using MinHeap = priority_queue<T, vector<T>, greater<T> >;
template <class T, class U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
  os << p.first << ',' << p.second;
  return os;
}
template <class T, class U>
istream& operator>>(istream& is, pair<T, U>& p) {
  is >> p.first >> p.second;
  return is;
}
template <class T>
ostream& operator<<(ostream& os, const vector<T>& vec) {
  for (int i = 0; i < vec.size(); i++) {
    os << vec[i];
    if (i + 1 < vec.size()) os << ' ';
  }
  return os;
}
template <class T>
istream& operator>>(istream& is, vector<T>& vec) {
  for (int i = 0; i < vec.size(); i++) is >> vec[i];
  return is;
}
void fastio() {
  cin.tie(0);
  ios::sync_with_stdio(0);
  cout << fixed << setprecision(20);
}
namespace Math {
const long long MOD = 1000000007ll;
struct ModInt {
  long long val;
  ModInt() : val(0ll) {}
  ModInt(const long long& v) : val(((v % MOD) + MOD) % MOD) {}
  ModInt exp(long long y) const {
    if (!y) return ModInt(1ll);
    ModInt a = exp(y / 2ll);
    a *= a;
    if (y & 1) a *= (*this);
    return a;
  }
  bool operator==(const ModInt& x) const { return val == x.val; }
  inline bool operator!=(const ModInt& x) const { return !(*this == x); }
  bool operator<(const ModInt& x) const { return val < x.val; }
  bool operator>(const ModInt& x) const { return val > x.val; }
  inline bool operator>=(const ModInt& x) const { return !(*this < x); }
  inline bool operator<=(const ModInt& x) const { return !(*this > x); }
  ModInt& operator+=(const ModInt& x) {
    if ((val += x.val) >= MOD) val -= MOD;
    return *this;
  }
  ModInt& operator-=(const ModInt& x) {
    if ((val += MOD - x.val) >= MOD) val -= MOD;
    return *this;
  }
  ModInt& operator*=(const ModInt& x) {
    (val *= x.val) %= MOD;
    return *this;
  }
  ModInt operator+(const ModInt& x) const { return ModInt(*this) += x; }
  ModInt operator-(const ModInt& x) const { return ModInt(*this) -= x; }
  ModInt operator*(const ModInt& x) const { return ModInt(*this) *= x; }
  friend istream& operator>>(istream& i, ModInt& x) {
    long long v;
    i >> v;
    x = v;
    return i;
  }
  friend ostream& operator<<(ostream& o, const ModInt& x) {
    o << x.val;
    return o;
  }
};
ModInt pow(ModInt a, long long x) {
  ModInt res = ModInt(1ll);
  while (x) {
    if (x & 1) res *= a;
    x >>= 1;
    a = a * a;
  }
  return res;
}
vector<ModInt> inv, fac, facinv;
ModInt nCr(int n, int r) {
  assert(!(n < r));
  assert(!(n < 0 || r < 0));
  return fac[n] * facinv[r] * facinv[n - r];
}
void init(int SIZE) {
  fac.resize(SIZE + 10);
  inv.resize(SIZE + 10);
  facinv.resize(SIZE + 10);
  fac[0] = ModInt(1ll);
  for (int i = 1; i <= SIZE; i++) fac[i] = fac[i - 1] * ModInt(i);
  inv[1] = ModInt(1ll);
  for (int i = 2; i <= SIZE; i++)
    inv[i] = ModInt(0ll) - ModInt(MOD / i) * inv[MOD % i];
  facinv[0] = ModInt(1ll);
  for (int i = 1; i <= SIZE; i++) facinv[i] = facinv[i - 1] * inv[i];
  return;
}
}  // namespace Math
namespace DS {
template <class T>
struct RangeSum {
  vector<T> vec;
  RangeSum() {}
  RangeSum(vector<T> elems) : vec(elems) {
    for (int i = 1; i < vec.size(); i++) {
      vec[i] += vec[i - 1];
    }
  }
  T sum(int l, int r) {
    if (l > r) return T(0);
    if (l == 0)
      return vec[r];
    else
      return vec[r] - vec[l - 1];
  }
};
template <class T, int N>
struct BIT {
  vector<T> bit;
  BIT() { bit = vector<T>(N + 1, T(0)); }
  void add(int i, T x) {
    i++;
    while (i <= N) {
      bit[i] += x;
      i += i & -i;
    }
    return;
  }
  T sum(int i) {
    i++;
    T res = T(0);
    while (i > 0) {
      res += bit[i];
      i -= i & -i;
    }
    return res;
  }
  T sum(int l, int r) {
    assert(l <= r);
    if (l == 0)
      return sum(r);
    else
      return sum(r) - sum(l - 1);
  }
};
}  // namespace DS
int N;
vector<int> x;
using namespace Math;
signed main() {
  fastio();
  cin >> N;
  init(100100);
  x.resize(N);
  for (int i = 0; i < N; i++) cin >> x[i];
  ModInt ans;
  for (int i = 0; i + 2 < N; i++) {
    for (int j = i + 1; j + 1 < N; j++) {
      int a = j - i - 1;
      ans += nCr(N - 1, a + 2) * fac[a] * fac[N - a - 3] * ModInt(x[j] - x[i]);
    }
    ans += nCr(N - 1, i) * fac[N - 2 - i] * fac[i] * ModInt(x[N - 1] - x[i]);
  }
  ans += fac[N - 1] * ModInt(x[N - 1] - x[N - 2]);
  cout << ans << endl;
  return 0;
}
