#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define lef(x) (x<<1)
#define rig(x) (lef(x)+1)
#define int long long
const ll MOD=1e9+7LL;
const int N=100100;
ll md(ll x){
	return ((x%MOD)+MOD)%MOD;
}
ll fastexpo(ll x, ll n)
{
	ll b=1LL;
	while(n)
	{
		if(n&1LL)
			b=md(b*x);
		x=md(x*x);
		n>>=1LL;
	}
	return b;
}
ll invfat[N],fat[N],a[N];
int32_t main()
{
    ios::sync_with_stdio(false);
    cin.tie(NULL);
    fat[0]=1;
    invfat[0]=1;
    for (int i = 1; i < N; ++i)
    {
    	fat[i]=md(fat[i-1]*i);
    	invfat[i]=fastexpo(fat[i],MOD-2);
    }
    int n;
    cin>>n;
    for (int i = 1; i <= n; ++i)
    {
    	cin>>a[i];
    }
    ll tot=0LL;
    ll rs=0LL;
    for (int i = 1; i <n; ++i)
    {
    	tot=md(tot+fastexpo(i,MOD-2));
    	// cout<<tot<<" "<<(a[i+1]-a[i])<<"\n";
    	rs=md(rs+(a[i+1]-a[i])*tot);
    }
    // cout<<rs<<"\n";
    rs=md(rs*fat[n-1]);
    cout<<rs<<"\n";
    return 0;   
}