# include<iostream>
# include <cstdio>
# include <algorithm>
# include <cstring>
# include <set>
using namespace std;

long long A[100100];
long long mi[100100];
const long long mod = 1e9+7;
long long m(long long x){
    long long ans = 1;
    long long temp = x;
    long long cnt = mod-2;
    while(cnt){
        if (cnt&1) ans=ans*temp%mod;
        temp = temp*temp%mod;
        cnt>>=1;
    }
    return ans;
}
int main(void){
    long long N;
    scanf("%lld",&N);
    mi[0] = 1;
    for (long long i=1;i<=N;i++) mi[i] = mi[i-1]*i%mod;
    long long temp = mi[N-1];
    long long anss = 0;
    long long t = 0;
    scanf("%lld",&A[1]);
    for (long long i=2;i<=N;i++){
        scanf("%lld",&A[i]);
        long long tt = A[i]-A[i-1];
        t+=temp*m(i-1);
        t%=mod;
        anss+=tt*t;
        anss%=mod;
    } 
    cout<<anss<<endl;
    return 0;
}