// https://atcoder.jp/contests/dwacon6th-prelims/tasks/dwacon6th_prelims_b
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define REP(i, n) FOR(i, 0, n)
#define REPR(i, n) for (int i = n - 1; i >= 0; i--)
#define FOR(i, s, n) for (int i = (s), i##_len = (n); i < i##_len; ++i)
#define ALL(obj) (obj).begin(), (obj).end()
#define ALLR(obj) (obj).rbegin(), (obj).rend()
#define DIV(a, b) ((a - 1) / b + 1)
const int MOD = 1e9 + 7;

template <int MOD> struct ModInt {
    static const int Mod = MOD;
    unsigned x;
    ModInt() : x(0) {}
    ModInt(signed sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; }
    ModInt(signed long long sig) { x = sig < 0 ? sig % MOD + MOD : sig % MOD; }
    int get() const { return (int)x; }
    ModInt &operator+=(ModInt that) {
        if ((x += that.x) >= MOD)
            x -= MOD;
        return *this;
    }
    ModInt &operator-=(ModInt that) {
        if ((x += MOD - that.x) >= MOD)
            x -= MOD;
        return *this;
    }
    ModInt &operator*=(ModInt that) {
        x = (unsigned long long)x * that.x % MOD;
        return *this;
    }
    ModInt &operator/=(ModInt that) { return *this *= that.inverse(); }
    ModInt operator+(ModInt that) const { return ModInt(*this) += that; }
    ModInt operator-(ModInt that) const { return ModInt(*this) -= that; }
    ModInt operator*(ModInt that) const { return ModInt(*this) *= that; }
    ModInt operator/(ModInt that) const { return ModInt(*this) /= that; }
    ModInt inverse() const {
        long long a = x, b = MOD, u = 1, v = 0;
        while (b) {
            long long t = a / b;
            a -= t * b;
            std::swap(a, b);
            u -= t * v;
            std::swap(u, v);
        }
        return ModInt(u);
    }
    bool operator==(ModInt that) const { return x == that.x; }
    bool operator!=(ModInt that) const { return x != that.x; }
    ModInt operator-() const {
        ModInt t;
        t.x = x == 0 ? 0 : Mod - x;
        return t;
    }
};
template <int MOD> ostream &operator<<(ostream &st, const ModInt<MOD> a) {
    st << a.get();
    return st;
};
template <int MOD> ModInt<MOD> operator^(ModInt<MOD> a, unsigned long long k) {
    ModInt<MOD> r = 1;
    while (k) {
        if (k & 1)
            r *= a;
        a *= a;
        k >>= 1;
    }
    return r;
}
typedef ModInt<MOD> mint;

template <int N, typename T, T M> struct factorial_mod {
    T mod[N + 1];
    T inv_mod[N + 1];

    constexpr factorial_mod() : mod(), inv_mod() {
        mod[0] = 1;
        for (int i = 0; i < N; ++i) {
            mod[i + 1] = (mod[i] * (i + 1)) % M;
        }
        inv_mod[N] = power(mod[N], M - 2);
        for (int i = N - 1; i >= 0; --i) {
            inv_mod[i] = (inv_mod[i + 1] * (i + 1)) % M;
        }
    }

    constexpr T power(T a, T b) {
        T r = 1;
        while (b > 0) {
            if ((b & 1) != 0)
                r = (r * a) % M;
            a = (a * a) % M;
            b >>= 1;
        }
        return r;
    }

    constexpr T permutation(T n, T r) { return (mod[n] * inv_mod[n - r]) % M; }
    constexpr T combination(T n, T r) {
        return (((mod[n] * inv_mod[r]) % M) * inv_mod[n - r]) % M;
    }
    constexpr T homogenious(T n, T r) {
        return (n == 0 and r == 0 ? 1 : combination(n + r - 1, r));
    }
};
factorial_mod<200000, long long, MOD> facmod;

// https://www.hamayanhamayan.com/entry/2020/01/11/223646
signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int N;
    cin >> N;
    vector<int> X(N);
    for (auto &x : X) {
        cin >> x;
    }
    // 足される回数の期待値
    vector<mint> dp(N - 1);
    mint tot = 0, ans = 0;
    REP(i, N - 1) {
        dp[i] = (tot + i + 1) / (i + 1);
        tot += dp[i];
        ans += mint(X[i + 1] - X[i]) * dp[i];
    }
    ans *= facmod.permutation(N - 1, N - 1);

    cout << ans << endl;

    return 0;
}


Measured memory_bytes: 1408