static void Method(string[] args)
{
long n = ReadLong();
long[] xs = ReadLongs();
long mask = 1000000000 + 7;
CaseCalculator calculator = new CaseCalculator(mask, n);
long[] divs = new long[n];
for (int i = 0; i < n; i++)
{
divs[i] = calculator.Reverse(i + 1);
}
long[] sums = new long[n];
sums[0] = divs[0];
for (int i = 1; i < n; i++)
{
sums[i] = (sums[i - 1] + divs[i]) % mask;
}
long res = 0;
for (int i = 0; i < n - 1; i++)
{
long dist = xs[i + 1] - xs[i];
res += dist * sums[i];
res %= mask;
}
for (int i = 1; i < n; i++)
{
res = (res * i) % mask;
}
WriteLine(res);
}
