#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pii> vpii;
typedef vector<pll> vpll;

ll MOD=1e9+7;

ll modinv(ll x)
{
    ll res=1;
    ll pw=MOD-2;
    while(pw>0)
    {
        if(pw%2) res=(res*x)%MOD;
        pw/=2;
        x=(x*x)%MOD;
    }
    return res;
}

ll t[100009];
ll fact=1;
ll n;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin>>n;
    ll sum=0;
    ll ans=0;
    for(ll i=0; i<n; i++)
    {
        cin>>t[i];
        if(i==0) continue;
        fact=(fact*i)%MOD;
        ll va=t[i]-t[i-1];
        sum+=modinv(i);
        ll pl=(sum*va)%MOD;
        ans=(ans+pl)%MOD;
    }
    ans=(ans*fact)%MOD;
    cout<<ans<<endl;
    return 0;
}
