#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
typedef long long ll;
const long long INF = 1e18;
const int MOD = 1000000007;

long long modinv(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;
}

ll fact(ll k){
    ll res=1;
    rep(i,k){
        res*=i+1;
        res%=MOD;
    }
    return res;
}


int main(){
    ll N;
    ll res=0;
    cin>>N;
    ll fac=fact(N-1);
    vector<ll> x(N);
    rep(i,N) cin>>x[i];
    rep(i,N-1){
        res+=((x[N-1]-x[i])*fac % MOD) * modinv(i+1,MOD);
        res%=MOD;
    }
    cout<<res<<endl;
    return 0;
}