import std.stdio, std.conv, std.functional, std.string;
import std.algorithm, std.array, std.container, std.range, std.typecons;
import std.bigint, std.numeric, std.math, std.random;
import core.bitop;

string FMT_F = "%.10f";

static File _f;
void file_io(string fn) { _f = File(fn, "r"); }
static string[] s_rd;
T _RD(T = long)() { while(!s_rd.length) s_rd = readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
T _RD(T = long)(File f) { while(!s_rd.length) s_rd = f.readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; }
T[] _RDA(T = long)(T fix = 0) { auto r = readln.chomp.split.to!(T[]); r[] += fix; return r; }
T[] _RDA(T = long)(File f, T fix = 0) { auto r = f.readln.chomp.split.to!(T[]); r[] += fix; return r; }
T RD(T = long)() { if (_f.isOpen) return _RD!T(_f); else return _RD!T; }
T[] RDA(T = long)(T fix = 0) { if (_f.isOpen)  return _RDA!T(_f, fix); else return _RDA!T(fix); }

size_t[] MAKE_IDX(alias less = "a < b", Range)(Range range) { auto idx = new size_t[](range.length); makeIndex!(less)(range, idx); return idx;}
size_t MIN_POS(alias less = "a < b", Range)(Range range) { auto r = minPos!(less)(range); return range.length - r.length; }

void chmin(T)(ref T x, T y) { x = min(x, y); } void chmax(T)(ref T x, T y) { x = max(x, y); }
bool inside(T)(T x, T b, T e) { return x >= b && x < e; }
long lcm(long x, long y) { return x * (y / gcd(x, y)); }

long mod = 10^^9 + 7;
//long mod = 998244353;
//long mod = 1_000_003;
void moda(ref long x, long y) { x = (x + y) % mod; }
void mods(ref long x, long y) { x = ((x + mod) - (y % mod)) % mod; }
void modm(ref long x, long y) { x = (x * y) % mod; }
void modpow(ref long x, long y) { if (!y) { x = 1; return; } auto t = x; x.modpow(y>>1); x.modm(x); if (y&1) x.modm(t); }

long modinv(long a) {
    long b = mod, u = 1, v = 0;
    while (b) {
        long t = a / b;
        a -= t * b; swap(a, b);
        u -= t * v; swap(u, v);
    }
    u %= mod;
    if (u < 0) u += mod;
    return u;
}

void modd(ref long x, long y)
{
	x.modm(modinv(y));
}

void main()
{
	auto N = RD;
	auto x = RDA;

	auto fact = new long[](N+1);
	fact[0] = 1;
	foreach (i; 0..N)
	{
		fact[i+1] = fact[i] * (i+1);
	}
	auto fact_s = new long[](N+1);

	foreach (i; 0..N)
	{
		foreach (j; 0..i+1)
		{
			long pat = fact[i];
			pat.modd(fact[i-j]);
			fact_s[i].moda(pat);
		}
	}

	debug writeln(fact);
	debug writeln(fact_s);

	if (N == 2)
	{
		writeln(x[1] - x[0]);
	}
	else
	{
		long ans;
		foreach (i; 0..N-1)
		{
			foreach (j; i+1..N)
			{
				auto d = j-i-1;
				auto cnt = N-3;
				if (j == N-1)
				{
					cnt = max(N-2, i);
				}
				long pat = 1;
				pat.modm(fact_s[cnt]);
				pat.modd(fact[d]);
				pat.modm(x[j]-x[i]);
				ans.moda(pat);
				debug writeln("i:", i, " j:", j, " ans:", ans);
			}

		}
		writeln(ans);
	}
	
	stdout.flush;
	debug readln;
}
