#include <iostream>
#include <algorithm>
#include <cstdio>
#include <vector>
 
using namespace std;
 
#define REP(i, n) for(int i = 0; i < (int)(n); i++)
 
int getInt() {
    int s;
    scanf("%d", &s);
    return s;
}
 
typedef long long ll;
const ll mod = 1000000007;
 
ll x[100000];
ll f[100000 + 10];
ll rf[100000 + 10];
 
ll mpow(ll b, ll e) {
    ll ans = 1;
    while(e){
        if(e % 2 == 1) ans = (ans * b) % mod;
        b = (b * b) % mod;
        e = e / 2;
    }
    return ans;
}
 
int main(){
    const int n = getInt();
    REP(i,n) x[i] = getInt();
 
    f[0] = 1;
    REP(i,n) f[i + 1] = f[i] * (i + 1) % mod;

    ll ans = 0;
    ll acc = 0;
    for(int i = 1; i < n; i++) {
        acc = (acc + mpow(i, mod - 2)) % mod;
        ans = (ans + (x[i] - x[i - 1]) * acc % mod) % mod;
    }
 
    ans = ans * f[n - 1] % mod;
 
    printf("%lld\n", ans);
 
    return 0;
}