using System;
using System.Linq;
class AC
{
    static void Main()
    {
        var (N, K) = Csin.Input<int, long>();
        var A = Console.ReadLine().Split().Select(long.Parse).ToArray();
        const int MOD = (int)1e9 + 7;
        long modpow(long x, int n)
        {
            if (n == 0) return 1L;
            return n % 2 == 0 ? modpow((x * x) % MOD, n / 2) % MOD : (x * modpow(x, n - 1)) % MOD;
        }
        var comb = new long[N];
        comb[0] = 1;
        for (var i = 1; i < N; i++) comb[i] = ((comb[i - 1] * (K + i)) % MOD * modpow(i, MOD - 2)) % MOD;
        long ans = 0;
        for (var i = 0; i < N; i++)
        {
            ans += ((comb[i] * comb[N - 1 - i]) % MOD * A[i]) % MOD;
            ans %= MOD;
        }
        Console.WriteLine(ans);
    }
}
static class Csin
{
    public static string[] StrArray() => Console.ReadLine().Split();
    public static string[] StrArray(char separator) => Console.ReadLine().Split(separator);

    private static T Conv<T>(string value) => (T)Convert.ChangeType(value, typeof(T));
    public static (T, U) ReadTuple<T, U>(string[] input) => (Conv<T>(input[0]), Conv<U>(input[1]));
    public static (T, U, V) ReadTuple<T, U, V>(string[] input) => (Conv<T>(input[0]), Conv<U>(input[1]), Conv<V>(input[2]));
    public static (T, U, V, W) ReadTuple<T, U, V, W>(string[] input) => (Conv<T>(input[0]), Conv<U>(input[1]), Conv<V>(input[2]), Conv<W>(input[3]));
    public static (T, U, V, W, X) ReadTuple<T, U, V, W, X>(string[] input) => (Conv<T>(input[0]), Conv<U>(input[1]), Conv<V>(input[2]), Conv<W>(input[3]), Conv<X>(input[4]));

    public static (T, U) Input<T, U>() => ReadTuple<T, U>(StrArray());
    public static (T, U, V) Input<T, U, V>() => ReadTuple<T, U, V>(StrArray());
    public static (T, U, V, W) Input<T, U, V, W>() => ReadTuple<T, U, V, W>(StrArray());
    public static (T, U, V, W, X) Input<T, U, V, W, X>() => ReadTuple<T, U, V, W, X>(StrArray());
}