n=int(input())
x=list(map(int,input().split()))
mod=pow(10,9)+7

def cmb(n,r,mod):
  if (r<0 or r>n):
    return 0
  r=min(r,n-r)
  return g1[n]*g2[r]*g2[n-r]%mod
g1=[1,1] # g1[i]=i! % mod　:階乗
g2=[1,1] # g2[i]=(i!)^(-1) % mod　:階乗の逆元
inverse=[0,1]
for i in range(2,n+1):
  g1.append((g1[-1]*i)%mod)
  inverse.append((-inverse[mod%i]*(mod//i))%mod)
  g2.append((g2[-1]*inverse[-1])%mod)
ans=0
for i in range(n-1):
  ans+=(x[n-1]-x[i])*g1[n-1]*pow(i+1,mod-2,mod)
  ans%=mod
print(ans)
