
import java.util.Arrays;
import java.util.Scanner;

public class Main {
    static final Scanner sc    = new Scanner(System.in);
    static final int     MOD   = (int) 1E9 + 7;
    static final long    INF_L = (long) 4E18;
    static final int     INF   = Integer.MAX_VALUE;
    
    public static void main(String[] args) {
        COMinit();
        int N = nint();
        int[] x = nints(N, 1, 0);
        
        long ans = 0;
        int n = 0;
        for (int i = N-1; i >= 1; i--) {
            long diff = x[N] - x[i];
            long multi = 0;
            for (int r = 0; r <= n; r++) {
                long tempMulti = fac[N-2-r] * COM(n, r);
                tempMulti %= MOD;
                tempMulti *= fac[r];
                tempMulti %= MOD;
                multi += tempMulti;
                multi %= MOD;
            }
            ans += diff * multi;
            ans %= MOD;
            n++;
        }
        System.out.println(ans);
    }
    
    static final int MAX = 700000;
    static long[] fac = new long[MAX], finv = new long[MAX], inv = new long[MAX];

    static void COMinit() {
        fac[0] = fac[1] = 1;
        finv[0] = finv[1] = 1;
        inv[1] = 1;
        for (int i = 2; i < MAX; i++){
            fac[i] = fac[i - 1] * i % MOD;
            inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
            finv[i] = finv[i - 1] * inv[i] % MOD;
        }
    }

    static long COM(int n, int k){
        if (fac[0] == 0) {
            throw new IllegalStateException("COMinit()が呼ばれていません");
        }
        if (n < k) return 0;
        if (n < 0 || k < 0) return 0;
        return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
    }
    
    @Deprecated
    static int nint() {
        return sc.nextInt();
    }

    @Deprecated
    static int[] nints(int N) {
        return nints(N, 0, 0);
    }

    @Deprecated
    private static int[] nints(int N, int padL, int padR) {
        int[] a = new int[padL + N + padR];
        for (int i = 0; i < N; i++)
            a[padL + i] = nint();
        return a;
    }

    static long nlong() {
        return sc.nextLong();
    }

    static long[] nlongs(int N) {
        return nlongs(N, 0, 0);
    }

    static long[] nlongs(int N, int padL, int padR) {
        long[] a = new long[padL + N + padR];
        for (int i = 0; i < N; i++)
            a[padL + i] = nlong();
        return a;
    }

    static double ndouble() {
        return sc.nextDouble();
    }

    static double[] ndoubles(int N) {
        return ndoubles(N, 0, 0);
    }

    static double[] ndoubles(int N, int padL, int padR) {
        double[] d = new double[N + padL + padR];
        for (int i = 0; i < N; i++) {
            d[padL + i] = ndouble();
        }
        return d;
    }

    static String nstr() {
        return sc.next();
    }

    static char[] nchars() {
        return sc.next().toCharArray();
    }

    static char[] nchars(int padL, int padR) {
        char[] temp = sc.next().toCharArray();
        char[] ret = new char[temp.length + padL + padR];
        System.arraycopy(temp, 0, ret, padL, temp.length);
        return ret;
    }

    static char[][] nchars2(int H, int W) {
        return nchars2(H, W, 0, 0);
    }

    static char[][] nchars2(int H, int W, int padLU, int padRD) {
        char[][] a2 = new char[H + padLU + padRD][W + padLU + padRD];
        for (int i = 0; i < H; i++)
            System.arraycopy(nchars(), 0, a2[padLU + i], padLU, W);
        return a2;
    }

    static long min(long... ls) {
        return Arrays.stream(ls).min().getAsLong();
    }

    static long max(long... ls) {
        return Arrays.stream(ls).max().getAsLong();
    }

    static long abs(long a) {
        return Math.abs(a);
    }
}
