#include <bits/stdc++.h>
#include <cassert>
typedef long long int ll;
using namespace std;

// --- DEBUG begin --- cut here ---
template <class... Args>
string dbgFormat(const char* fmt, Args... args) {
  size_t len = snprintf(nullptr, 0, fmt, args...);
  char buf[len + 1];
  snprintf(buf, len + 1, fmt, args...);
  return string(buf);
}

template <class Head>
void dbgLog(Head&& head) {
  cerr << head << endl;
}

template <class Head, class... Tail>
void dbgLog(Head&& head, Tail&&... tail)
{
  cerr << head << " ";
  dbgLog(forward<Tail>(tail)...);
}

#if DEBUG
  #define DLOG(...)        dbgLog(__VA_ARGS__)
  #define DFMT(...)        cerr << dbgFormat(__VA_ARGS__) << endl
  #define DCALL(func, ...) func(__VA_ARGS__)
#else
  #define DLOG(...)
  #define DFMT(...)
  #define DCALL(func, ...)
#endif

// operator<< definitions for some classes

template <typename T1, typename T2>
ostream& operator<< (ostream& os, const pair<T1,T2>& p) {
  os << "(" << p.first << ", " << p.second << ")";
  return os;
}

template <typename T>
ostream& operator<< (ostream& os, const vector<T>& v) {
  os << '[';
  for (auto it = v.begin(); it != v.end(); it++) {
    if (it != v.begin()) os << ", ";
    os << *it;
  }
  os << ']';

  return os;
}

template <typename T, typename T2, typename T3>
ostream& operator<< (ostream& os, const priority_queue<T, T2, T3>& orig) {
  priority_queue<T, T2, T3> pq(orig);
  bool first = true;
  os << '[';
  while (!pq.empty()) {
    T x = pq.top(); pq.pop();
    if (!first) os << ", ";
    os << x;
    first = false;
  }
  return os << ']';
}
// --- DEBUG end --- cut here ---



// --- MOD begin --- cut here ---

ll MOD = 1e9 + 7;
// ll MOD = 998244353;

// g = eGCD(a, b, s, t)  --->  sa + tb = g
constexpr ll eGCD(ll a, ll b, ll& s, ll& t) {
  if (a == 0) {
    s = 0;
    t = 1;
    return b;
  }
  ll u = 0;
  ll g = eGCD(b % a, a, t, u);
  s = u - (b / a) * t;
  return g;
}

constexpr ll gcd(ll a, ll b) {
  ll dummy1 = 0;
  ll dummy2 = 0;
  return eGCD(a, b, dummy1, dummy2);
}

struct Fp {
  ll val;

  Fp(ll t = 0) :
    val(t < 0 ? MOD + t % MOD : t >= MOD ? t % MOD : t) {}

  Fp& operator +=(const Fp& t) {
    val += t.val;
    if (val >= MOD) val -= MOD;
    return *this;
  }

  Fp& operator -=(const Fp& t) {
    val -= t.val;
    if (val < 0) val += MOD;
    return *this;
  }

  Fp& operator *=(const Fp& t) {
    val = (val * t.val) % MOD;
    return *this;
  }

  Fp inv() const {
    if (val == 0) {
      cerr << "inv() is called for zero." << endl;
      exit(1);
    }
    ll u = 0;
    ll v = 0;
    eGCD(val, MOD, u, v);
    return Fp(u);
  }

  Fp& operator /=(const Fp& t) {
    return (*this) *= t.inv();
  }

  Fp operator +(const Fp& t) const { return Fp(val) += t; }
  Fp operator -(const Fp& t) const { return Fp(val) -= t; }
  Fp operator *(const Fp& t) const { return Fp(val) *= t; }
  Fp operator /(const Fp& t) const { return Fp(val) /= t; }
  Fp operator -() const { return Fp(-val); }

  bool operator ==(const Fp& t) const { return val == t.val; }
  bool operator !=(const Fp& t) const { return val != t.val; }
  
  operator ll() const { return val; }

};

class Comb {
  int nMax;
  vector<Fp> vFact;
  vector<Fp> vInvFact;
public:
  Comb(int nm) : nMax(nm), vFact(nm+1), vInvFact(nm+1) {
    vFact.at(0) = 1;
    for (int i = 1; i <= nMax; i++) vFact.at(i) = i * vFact.at(i-1);
    vInvFact.at(nMax) = vFact.at(nMax).inv();
    for (int i = nMax; i >= 1; i--) vInvFact.at(i-1) = i * vInvFact.at(i);
  }
  Fp fact(int n) { return vFact.at(n); }
  Fp comb(int n, int r) {
    return vFact.at(n) * vInvFact.at(r) * vInvFact.at(n-r);
  }
  // The number of permutation extracting r from n.
  Fp perm(int n, int r) {
    return vFact.at(n) * vInvFact.at(n-r);
  }
};

/* 
   Power function    power(a, b) == a^b
   Speed is O(log b).
   The same source code can be used for integers by replacing
   Fp with int etc.  Unfortunately, replacing Fp with auto does not
   make the function generic for int and Fp.
 */
Fp power(Fp a, ll b) {
  Fp twoPow = a;
  Fp rv = 1;
  while (b > 0) {
    if (b & 1LL) rv *= twoPow;
    twoPow *= twoPow;
    b >>= 1;
  }
  return rv;
}

// --- MOD end --- cut here ---



int main(int argc, char *argv[]) {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << setprecision(20);

  ll N; cin >> N;
  vector<ll> X(N);
  for (ll i = 0; i < N; i++) cin >> X.at(i);
  Comb cb(N);
  Fp mult = cb.fact(N-1);
  Fp ans = 0;
  Fp s = 0;
  for (ll k = 0; k < N-1; k++) {
    s = s + mult / Fp(k + 1);
    DLOG("k", k, s);
    ans = ans + s * Fp(X.at(k+1) - X.at(k));
  }
  cout << ans << endl;

  return 0;
}



Measured memory_bytes: 2560