#include <bits/stdc++.h>
using namespace std;
typedef int64_t ll;
const int MOD=1e9+7;
int modinv(ll a)
{
  ll b=MOD,u=1,v=0;
  while(b)
  {
    ll t=a/b;
    a-=t*b;swap(a,b);
    u-=t*v;swap(u,v);
  }
  u%=MOD; 
  if(u<0)u+=MOD;
  return u;
}
int main()
{
  ll answer=0,N;
  cin>>N;
  vector<ll> s(N,0);
  for(int i=0;i<N;i++) cin>>s.at(i);
  for(int i=0;i<N-1;i++) answer+=((s.at(N-1)-s.at(i))*modinv(i+1))%MOD;
  for(int i=1;i<N;i++) answer=(answer*i)%MOD;
  cout<<answer<<endl;
}