#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<(n); i++)
#define itrep(type, it, t) for(type::iterator it=t.begin(); it!=t.end(); it++)
using namespace std;

#define MOD (1000000007)

long long invmodp(long long a, long long m) {
    long long b = m, u = 1, v = 0;
    while (b) {
        long long t = a / b;
        a -= t * b; swap(a, b);
        u -= t * v; swap(u, v);
    }
    u %= m; 
    if (u < 0) u += m;
    return u;
}

int main(void) {

    int N;
    cin >> N;
    long long X[N];
    long long fact = 1;
    rep(i, N) {
        cin >> X[i];
        fact = fact * max(1, i) % MOD;
    }

    long long ans = 0;
    long long inv = 0;
    rep(i, N-1) {
        long long diff = X[i+1] - X[i];
        inv = inv + invmodp(i+1, MOD) % MOD;
        long long add = diff * inv % MOD;
        ans = (ans + add) % MOD;
    }

    cout << (ans*fact)%MOD;
    return 0;
}