using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Numerics;
using System.Threading.Tasks;
using static System.Console;
using static System.Math;
using static Func;
class Z { static void Main() => new K(); }
class K
{
	int F => int.Parse(Str);
	long FL => long.Parse(Str);
	int[] G => Strs.Select(int.Parse).ToArray();
	uint[] GU => Strs.Select(uint.Parse).ToArray();
	decimal[] GD => Strs.Select(decimal.Parse).ToArray();
	long[] GL => Strs.Select(long.Parse).ToArray();
	string Str => ReadLine();
	string[] Strs => Str.Split(new char[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries);
	static ulong One(int k) => 1ul << k;
	static ulong All(int k) => One(k) - 1;
	static bool Has(ulong s, int k) => (s & One(k)) != 0;
	const int MOD = 1000000007;
	public K()
	{
		SetOut(new StreamWriter(OpenStandardOutput()) { AutoFlush = false });
		Solve();
		Out.Flush();
	}
	void Solve()
	{
		var N = F;
		var x = G;
		var inv = new long[N + 1];
		for (var i = 1; i <= N; i++) inv[i] = Inverse(i, MOD);
		var f = 1L;
		for (var i = 2; i < N; ++i) f = f * i % MOD;
		var s = 0L;
		for (var i = 0; i < N; i++)
			for (var j = i + 1; j + 1 < N; j++)
			{
				var t = (x[j] - x[i]) * inv[j - i] % MOD * inv[j - i + 1] % MOD;
				// WriteLine($"{x[i]} -> {x[j]}: {t * f % MOD}");
				s = (s + t) % MOD;
			}
		for (var i = 0; i + 1 < N; i++)
		{
			var j = N - 1;
			var t = (x[j] - x[i]) * inv[j - i] % MOD;
			// WriteLine($"{x[i]} -> {x[j]}: {t * f % MOD}");
			s = (s + t) % MOD;
		}
		WriteLine(s * f % MOD);
	}
}
static class Func
{
	public const int Inf = 1073741789;
	public const long InfL = 4011686018427387913L;
	public static T[] ConstantArray<T>(int n, T val) { var a = new T[n]; for (var i = 0; i < n; i++) a[i] = val; return a; }
	public static T[,] ConstantArray<T>(int n, int m, T val) { var a = new T[n, m]; for (var i = 0; i < n; i++) for (var j = 0; j < m; j++) a[i, j] = val; return a; }
	public static T[,,] ConstantArray<T>(int n, int m, int l, T val) { var a = new T[n, m, l]; for (var i = 0; i < n; i++) for (var j = 0; j < m; j++) for (var k = 0; k < l; k++) a[i, j, k] = val; return a; }
	public static T[] MakeArray<T>(int n, Func<int, T> f) { var a = new T[n]; for (var i = 0; i < n; i++) a[i] = f(i); return a; }
	public static T[,] MakeArray<T>(int n, int m, Func<int, int, T> f) { var a = new T[n, m]; for (var i = 0; i < n; i++) for (var j = 0; j < m; j++) a[i, j] = f(i, j); return a; }
	public static T[,,] MakeArray<T>(int n, int m, int l, Func<int, int, int, T> f) { var a = new T[n, m, l]; for (var i = 0; i < n; i++) for (var j = 0; j < m; j++) for (var k = 0; k < l; k++) a[i, j, k] = f(i, j, k); return a; }
	public static T[] Recurse<T>(int n, T a0, Func<int, T, T> f) { var a = new T[n]; a[0] = a0; for (var i = 1; i < n; i++) a[i] = f(i, a[i - 1]); return a; }
	public static T[] Accumulate<T>(IList<T> a, T zero, Func<T, T, T> f) { var s = new T[a.Count + 1]; s[0] = zero; for (var i = 0; i < a.Count; i++) s[i + 1] = f(s[i], a[i]); return s; }
	public static int FirstBinary(int min, int max, Predicate<int> pred)
	{
		while (min < max)
		{
			var mid = (min + max) / 2;
			if (pred(mid)) max = mid;
			else min = mid + 1;
		}
		return min;
	}
	public static long GCD(long a, long b)
	{
		var n = (ulong)Abs(a); var m = (ulong)Abs(b);
		if (n == 0) return (long)m; if (m == 0) return (long)n;
		int zm = 0, zn = 0;
		while ((n & 1) == 0) { n >>= 1; zn++; }
		while ((m & 1) == 0) { m >>= 1; zm++; }
		while (m != n)
		{
			if (m > n) { m -= n; while ((m & 1) == 0) m >>= 1; }
			else { n -= m; while ((n & 1) == 0) n >>= 1; }
		}
		return (long)n << Min(zm, zn);
	}
	public static long Mod(long a, long mod) => (a % mod + mod) % mod;
	public static long Inverse(long a, long mod) => Mod(SolveLinear(Mod(a, mod), mod)[0], mod);
	public static long Pow(long a, long b, long mod)
	{
		var p = 1L;
		var x = a;
		while (b > 0)
		{
			if ((b & 1) == 1) p = (p * x) % mod;
			b >>= 1;
			x = (x * x) % mod;
		}
		return p;
	}
	public static long[] SolveLinear(long n, long m)
	{
		var A = new long[,] { { n < 0 ? -1 : 1, 0 }, { 0, m < 0 ? -1 : 1 } };
		n = Abs(n); m = Abs(m);
		while (m > 0)
		{
			long q = n / m, r = n % m;
			n = m; m = r;
			for (var i = 0; i < 2; i++)
			{
				var x = A[i, 1];
				A[i, 1] = A[i, 0] - q * x;
				A[i, 0] = x;
			}
		}
		return new long[] { A[0, 0], A[1, 0] };
	}
	public static int CombineHashCodes(int h1, int h2) => (((h1 << 5) + h1) ^ h2);
	public static int[] GetFact(int lim, int mod)
	{
		var f = new int[lim];
		f[0] = 1;
		for (var i = 1; i < lim; i++) f[i] = (int)((long)f[i - 1] * i % mod);
		return f;
	}
	public static int[] GetInvFact(int lim, int mod)
	{
		var fc = 1;
		for (var i = 2; i < lim; i++) fc = (int)((long)fc * i % mod);
		return GetInvFact(lim, fc, mod);
	}
	// GetInvFact(n, (n-1)! mod p, p) gives {1, 1/2, ..., 1/(n-1)!} mod p
	public static int[] GetInvFact(int lim, int fc_of_lim_m_1, int mod)
	{
		var ifc = new int[lim];
		ifc[lim - 1] = (int)Inverse(fc_of_lim_m_1, mod);
		for (var i = lim - 1; i >= 1; i--) ifc[i - 1] = (int)((long)ifc[i] * i % mod);
		return ifc;
	}
	public static Comparison<T> DefaultComparison<T>() => (x, y) => Comparer<T>.Default.Compare(x, y);
	public static Comparison<T> ToComparison<T>(this IComparer<T> comp) => comp == null ? DefaultComparison<T>() : (x, y) => comp.Compare(x, y);
}
class PriorityQueue<T> : IEnumerable<T>, ICollection, IEnumerable, ICloneable
{
	Comparison<T> comp;
	List<T> list;
	public int Count { get; private set; } = 0;
	public bool IsEmpty => Count == 0;
	public PriorityQueue(IEnumerable<T> source) : this((Comparison<T>)null, 0, source) { }
	public PriorityQueue(int capacity = 4, IEnumerable<T> source = null) : this((Comparison<T>)null, capacity, source) { }
	public PriorityQueue(IComparer<T> comp, IEnumerable<T> source) : this(comp.ToComparison(), source) { }
	public PriorityQueue(IComparer<T> comp, int capacity = 4, IEnumerable<T> source = null) : this(comp.ToComparison(), source) { list.Capacity = capacity; }
	public PriorityQueue(Comparison<T> comp, IEnumerable<T> source) : this(comp, 0, source) { }
	public PriorityQueue(Comparison<T> comp, int capacity = 4, IEnumerable<T> source = null) { this.comp = comp ?? Func.DefaultComparison<T>(); list = new List<T>(capacity); if (source != null) foreach (var x in source) Enqueue(x); }
	/// <summary>
	/// add an item
	/// this is an O(log n) operation
	/// </summary>
	/// <param name="x">item</param>
	public void Enqueue(T x)
	{
		var pos = Count++;
		list.Add(x);
		while (pos > 0)
		{
			var p = (pos - 1) / 2;
			if (comp(list[p], x) <= 0) break;
			list[pos] = list[p];
			pos = p;
		}
		list[pos] = x;
	}
	/// <summary>
	/// return the minimum element and remove it
	/// this is an O(log n) operation
	/// </summary>
	/// <returns>the minimum</returns>
	public T Dequeue()
	{
		var value = list[0];
		var x = list[--Count];
		list.RemoveAt(Count);
		if (Count == 0) return value;
		var pos = 0;
		while (pos * 2 + 1 < Count)
		{
			var a = 2 * pos + 1;
			var b = 2 * pos + 2;
			if (b < Count && comp(list[b], list[a]) < 0) a = b;
			if (comp(list[a], x) >= 0) break;
			list[pos] = list[a];
			pos = a;
		}
		list[pos] = x;
		return value;
	}
	/// <summary>
	/// look at the minimum element
	/// this is an O(1) operation
	/// </summary>
	/// <returns>the minimum</returns>
	public T Peek() => list[0];
	public IEnumerator<T> GetEnumerator() { var x = (PriorityQueue<T>)Clone(); while (x.Count > 0) yield return x.Dequeue(); }
	void CopyTo(Array array, int index) { foreach (var x in this) array.SetValue(x, index++); }
	public object Clone() { var x = new PriorityQueue<T>(comp, Count); x.Count = Count; x.list.AddRange(list); return x; }
	public void Clear() { list = new List<T>(); Count = 0; }
	public void TrimExcess() => list.TrimExcess();
	/// <summary>
	/// check whether item is in this queue
	/// this is an O(n) operation
	/// </summary>
	public bool Contains(T item) => list.Contains(item);
	IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
	void ICollection.CopyTo(Array array, int index) => CopyTo(array, index);
	bool ICollection.IsSynchronized => false;
	object ICollection.SyncRoot => this;
}