/**
 *    author  : 𝒌𝒚𝒐𝒎𝒖𝒌𝒚𝒐𝒎𝒖𝒑𝒖𝒓𝒊𝒏
 *    created : 2020-01-11 19:30:36
**/

#include <iostream>
#include <deque>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <complex>
#include <numeric>
#include <bitset>
#include <cassert>
#include <cctype>
#include <iomanip>
#include <random>
#include <utility>
#include <chrono>

using namespace std;

using int64 = long long;

template<class T> std::ostream& operator<<(std::ostream& os, const std::vector<T>& vec) { os << '{'; size_t n = vec.size(); for (size_t i = 0; i < n; ++i) { os << vec[i]; if (i != n - 1) os << ','; } os << '}'; return os; }
template<class T, class U> std::ostream& operator<<(std::ostream& os, const std::pair<T, U>& p) { return os << '{' << p.first << " " << p.second << '}'; }
template<class T> std::istream& operator>>(std::istream& is, std::vector<T>& vec) { size_t n = vec.size(); for (size_t i = 0; i < n; ++i) is >> vec[i]; return is; }

#ifdef LOCAL
#define debug(_) cerr << #_ << ": " << (_) << '\n'
#else
#define debug(_) 1728
#endif

constexpr int64 MOD = 1e9 + 7;

class Combination {
 public:
  constexpr Combination() { Build(); }
  static constexpr int mod_ = 1000000007;
  static constexpr int n_ = 200;
  struct LookupTable {
    int64 factorial_[n_];
    int64 inverse_[n_];
    int64 finverse_[n_];
  };
  LookupTable lt{};

  // return nCk
  constexpr int64 Get(int n, int k) const noexcept {
    if (n < k || n < 0 || k < 0) return 0;
    return lt.factorial_[n] * (lt.finverse_[k] * lt.finverse_[n - k] % mod_) %
           mod_;
  }

 private:
  constexpr void Build() noexcept {
    lt.factorial_[0] = 1;
    lt.factorial_[1] = 1;
    lt.finverse_[0] = 1;
    lt.finverse_[1] = 1;
    lt.inverse_[1] = 1;
    for (int i = 2; i < n_; ++i) {
      lt.factorial_[i] = lt.factorial_[i - 1] * i % mod_;
      lt.inverse_[i] = mod_ - lt.inverse_[mod_ % i] * (mod_ / i) % mod_;
      lt.finverse_[i] = lt.finverse_[i - 1] * lt.inverse_[i] % mod_;
    }
  }
};

Combination comb;

template <class T>
class CumulativeSum {
 public:
  CumulativeSum(const std::vector<T>& vec) : vec_(vec) { Build(); }

  // return sum of [left, right]
  T Get(int left, int right) {
    return sum_[right + 1] - sum_[left];    
  }

 private:
  std::vector<T> vec_;
  std::vector<T> sum_;

  void Build() {
    sum_.assign(vec_.size() + 1, static_cast<T>(0));
    for (size_t i = 0; i < vec_.size(); ++i) {
      sum_[i + 1] = sum_[i] + vec_[i];
    }
  }
};

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);

  int n; cin >> n;
  vector<int64> x(n); cin >> x;

  if (n > 2000) abort();

  vector<int64> diff(n + 1, 0LL);
  for (int i = 1; i < n; ++i) {
    diff[i] = x[i] - x[i - 1];
  }
  debug(diff);

  CumulativeSum<int64> cs(diff);

  int64 dis[n][n];

  for (int i = 0; i < n - 1; ++i) {
    for (int j = i + 1; j < n; ++j) {
      dis[i][j] = cs.Get(0, j) - cs.Get(0, i);
    }
  }
  // dis[i][j] : i から j にいくまでの距離
  int64 ans = 0;

  for (int i = 1; i <= n - 1; ++i) {
    for (int j = 1; j <= n - i; ++j) {
      ans += ((comb.lt.factorial_[n - 1] * comb.lt.factorial_[n - 1] % MOD) / j) / (j + 1) * dis[i - 1][i - 1 + j] % MOD;
      ans %= MOD;
    }
  }

  cout << ans << endl;

  return 0;
}