#include <bits/stdc++.h>
using namespace std;
template <class T>
void _R(T &x) {
  cin >> x;
}
void _R(int &x) { scanf("%d", &x); }
void _R(double &x) { scanf("%lf", &x); }
void _R(char &x) { scanf(" %c", &x); }
void _R(char *x) { scanf("%s", x); }
void R() {}
template <class T, class... U>
void R(T &head, U &...tail) {
  _R(head);
  R(tail...);
}
template <class T>
void _W(const T &x) {
  cout << x;
}
void _W(const int &x) { printf("%d", x); }
void _W(const double &x) { printf("%.16f", x); }
void _W(const char &x) { putchar(x); }
void _W(const char *x) { printf("%s", x); }
void WA(const int *a, int n) {
  for (int i = 0; i < n; _W(a[i++]))
    if (i != 0) putchar(' ');
  puts("");
}
template <class T>
void _W(const vector<T> &x) {
  for (auto i = x.begin(); i != x.end(); _W(*i++))
    if (i != x.cbegin()) putchar(' ');
}
void W() {}
template <class T, class... U>
void W(const T &head, const U &...tail) {
  _W(head);
  putchar(sizeof...(tail) ? ' ' : '\n');
  W(tail...);
}
template <class Iter>
ostream &_out(ostream &s, Iter b, Iter e) {
  s << "[";
  for (auto it = b; it != e; it++) s << (it == b ? "" : " ") << *it;
  return s << "]";
}
template <class A, class B>
ostream &operator<<(ostream &s, const pair<A, B> &p) {
  return s << "(" << p.first << ", " << p.second << ")";
}
template <class T>
ostream &operator<<(ostream &s, const vector<T> &c) {
  return _out(s, begin(c), end(c));
}
template <class T, size_t N>
ostream &operator<<(ostream &s, const array<T, N> &c) {
  return _out(s, begin(c), end(c));
}
template <class T>
ostream &operator<<(ostream &s, const set<T> &c) {
  return _out(s, begin(c), end(c));
}
template <class A, class B>
ostream &operator<<(ostream &s, const map<A, B> &c) {
  return _out(s, begin(c), end(c));
}
template <class T, class first = less<T>>
void sort_uniq(vector<T> &v, first f = first()) {
  sort(begin(v), end(v), f);
  v.resize(unique(begin(v), end(v)) - begin(v));
}
template <class T>
inline T bit(T x, int i) {
  return (x >> i) & 1;
}
template <class T>
inline bool chmax(T &a, const T &b) {
  return b > a ? a = b, true : false;
}
template <class T>
inline bool chmin(T &a, const T &b) {
  return b < a ? a = b, true : false;
}
template <class T>
using MaxHeap = priority_queue<T>;
template <class T>
using MinHeap = priority_queue<T, vector<T>, greater<T>>;
template <class T>
void _dump(const char *s, T &&head) {
  cerr << s << "=" << head << endl;
}
template <class T, class... Args>
void _dump(const char *s, T &&head, Args &&...tail) {
  for (int c = 0; *s != ',' || c != 0; cerr << *s++) {
    if (*s == '(' || *s == '[' || *s == '{') c++;
    if (*s == ')' || *s == ']' || *s == '}') c--;
  }
  cerr << "=" << head << ",";
  _dump(s + 1, tail...);
}
int f(int n) {
  int r = 1;
  for (int i = 1; i <= n; i++) {
    r *= i;
    r %= 1000000007;
  }
  return r;
}
int main(void) {
  cin.tie(0);
  int n;
  R(n);
  int m = f(n - 1);
  int x[n];
  for (int i = 0; i < int(n); i++) {
    R(x[i]);
  }
  double d = 1;
  double sum = 0;
  for (int i = 0; i < int(n - 1); i++) {
    sum += (x[i + 1] - x[i]) * d;
    d += 0.5;
  }
  long long ans = (long long)(sum * m);
  W(ans % 1000000007);
  return 0;
}
