// Generated by 1.1.6 https://github.com/kyuridenamida/atcoder-tools

#include <bits/stdc++.h>

using namespace std;

using i64 = long long;

const long long MOD = 1000000007;
const i64 INF = i64(1e18) + 7;


template <typename T>
bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

template <typename T>
bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}

template <i64 mod = MOD>
struct ModInt{
    i64 p;

    ModInt() : p(0){}
    ModInt(i64 x){p = x >= 0 ? x % mod : x + (-x + mod - 1) / mod * mod;}

    ModInt& operator+=(const ModInt& y){p = p + *y - ((p + *y) >= mod ? mod : 0); return *this;}
    ModInt& operator-=(const ModInt& y){p = p - *y + (p - *y < 0 ? mod : 0); return *this;}
    ModInt& operator*=(const ModInt& y){p = (p * *y) % mod; return *this;}
    ModInt& operator%=(const ModInt& y){if(y)p %= *y; return *this;}

    ModInt operator+(const ModInt& y) const{ModInt x = *this; return x += y;}
    ModInt operator-(const ModInt& y) const{ModInt x = *this; return x -= y;}
    ModInt operator*(const ModInt& y) const{ModInt x = *this; return x *= y;}
    ModInt operator%(const ModInt& y) const{ModInt x = *this; return x %= y;}

    friend ostream& operator<<(ostream& stream, const ModInt<mod>& x){
        stream << *x;
        return stream;
    }

    friend ostream& operator>>(ostream& stream, const ModInt<mod>& x){
        stream >> *x;
        return stream;
    }

    ModInt& operator++(){p = (p + 1) % mod; return *this;}
    ModInt& operator--(){p = (p - 1 + mod) % mod; return *this;}

    bool operator==(const ModInt& y) const{return p == *y;}
    bool operator!=(const ModInt& y) const{return p != *y;}

    const i64& operator*() const{return p;}
    i64& operator*(){return p;}

};

using mint = ModInt<>;

template <typename T>
struct DisjointSparseTable{
    function<T(T, T)> f;
    vector<vector<T>> v;

    DisjointSparseTable(vector<T>& inp, function<T(T, T)> f) : f(f){
        int n = inp.size();
        int b;
        for(b = 0; (1 << b) <= inp.size(); ++b);
        v.assign(b, vector<T>(n));
        for(int i = 0; i < n; ++i)
            v[0][i] = inp[i];
        for(int i = 1; i < b; ++i){
            int siz = 1 << i;
            for(int j = 0; j < n; j += siz << 1){
                int t = min(j + siz, n);
                v[i][t - 1] = inp[t - 1];
                for(int k = t - 2; k >= j; --k)
                    v[i][k] = f(inp[k], v[i][k + 1]);
                if(t >= n)
                    break;
                v[i][t] = inp[t];
                int r = min(t + siz, n);
                for(int k = t + 1; k < r; ++k)
                    v[i][k] = f(v[i][k - 1], inp[k]);
            }
        }
    }

    T get(int l, int r){
        if(l >= --r)
            return v[0][l];
        int p = 31 - __builtin_clz(l ^ r);
        return f(v[p][l], v[p][r]);
    }
};


void solve(long long n, std::vector<long long> x){

    auto mpow = [](auto x, i64 y){
     auto z = x;
     decltype(x) val = y & 1 ? x : decltype(x)(1);
     while(z *= z, y >>= 1)
      if(y & 1)
       val *= z;
     return val;
    };

    auto calc_fact = [mpow]{
     constexpr int N = 2e5;
     vector<mint> fact(N + 1, 1);
     vector<mint> inv(N + 1, 1);
     for(int i = 1; i < N; ++i){
      fact[i + 1] = fact[i] * (i + 1);
      inv[i + 1] = mpow(fact[i + 1], MOD - 2);
     }
     return make_pair(fact, inv);
    };

    vector<mint> fact, inv;
    tie(fact, inv) = calc_fact();

    vector<mint> v(n + 10, 0);
    v[0] = 1;
    v[1] = 1;
    for(int i = 2; i < n + 10; ++i)
        v[i] = mpow(mint(i), MOD - 2);

    DisjointSparseTable<mint> d(v, [](auto x, auto y){return x + y;});
	int cnt = 0;
    mint ans = 0;
    int m = n - 1;
    for(int j = 0; j < n; ++j){
        i64 dist = x[j] - x[j - 1];
        mint val = mint(dist) * fact[m];
        // ans += val * mpow(mint(j * (j - 1) / 2), MOD - 2);
        // ans += val * inv[j];
        if(1 == j + 1)
            continue;
        ans += val * d.get(1, j + 1);
        for(int i = 0; i < j; ++i){
            ++cnt;// ans += val * mpow(mint(j - i), MOD - 2);
        }
    }
    cout << cnt << endl;
}


signed main(){
    long long N;
    scanf("%lld",&N);
    std::vector<long long> x(N);
    for(int i = 0 ; i < N ; i++){
        scanf("%lld",&x[i]);
    }
    solve(N, std::move(x));
    return 0;
}
