using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using YukicoderContest255.Extensions;
using YukicoderContest255.Questions;

namespace YukicoderContest255.Questions
{
    public class QuestionB : AtCoderQuestionBase
    {
        public override IEnumerable<object> Solve(TextReader inputStream)
        {
            var (n, k) = inputStream.ReadValue<int, int>();
            var a = inputStream.ReadIntArray();
            var sum = Modular.Zero;

            var combinations = new Modular[n];
            combinations[0] = Modular.One;
            for (int i = 0; i + 1 < combinations.Length; i++)
            {
                combinations[i + 1] = combinations[i] * new Modular(k + i + 1) / new Modular(i + 1);
            }

            for (int i = 0; i < a.Length; i++)
            {
                var left = i + 1;
                var right = a.Length - i;
                sum += new Modular(a[i]) * combinations[left - 1] * combinations[right - 1];
            }
            yield return sum.Value;
        }

        public readonly struct Modular : IEquatable<Modular>, IComparable<Modular>
        {
            private const int DefaultMod = 1000000007;
            public int Value { get; }
            public static int Mod { get; set; } = DefaultMod;

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public Modular(long value)
            {
                if (unchecked((ulong)value) < unchecked((ulong)Mod))
                {
                    Value = (int)value;
                }
                else
                {
                    Value = (int)(value % Mod);
                    if (Value < 0)
                    {
                        Value += Mod;
                    }
                }
            }

            private Modular(int value) => Value = value;
            public static Modular Zero => new Modular(0);
            public static Modular One => new Modular(1);

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public static Modular operator +(Modular a, Modular b)
            {
                var result = a.Value + b.Value;
                if (result >= Mod)
                {
                    result -= Mod;    // 剰余演算を避ける
                }
                return new Modular(result);
            }

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public static Modular operator -(Modular a, Modular b)
            {
                var result = a.Value - b.Value;
                if (result < 0)
                {
                    result += Mod;    // 剰余演算を避ける
                }
                return new Modular(result);
            }

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public static Modular operator *(Modular a, Modular b) => new Modular((long)a.Value * b.Value);

            [MethodImpl(MethodImplOptions.AggressiveInlining)]
            public static Modular operator /(Modular a, Modular b) => a * Pow(b.Value, Mod - 2);

            // 需要は不明だけど一応
            public static bool operator ==(Modular left, Modular right) => left.Equals(right);
            public static bool operator !=(Modular left, Modular right) => !(left == right);
            public static bool operator <(Modular left, Modular right) => left.CompareTo(right) < 0;
            public static bool operator <=(Modular left, Modular right) => left.CompareTo(right) <= 0;
            public static bool operator >(Modular left, Modular right) => left.CompareTo(right) > 0;
            public static bool operator >=(Modular left, Modular right) => left.CompareTo(right) >= 0;

            public static implicit operator Modular(long a) => new Modular(a);
            public static explicit operator int(Modular a) => a.Value;
            public static explicit operator long(Modular a) => a.Value;

            public static Modular Pow(int a, int n)
            {
                switch (n)
                {
                    case 0:
                        return Modular.One;
                    case 1:
                        return a;
                    case int m when m >= 0: // ジャンプテーブル化はできなくなる
                        var p = Pow(a, m >> 1);             // m / 2
                        return p * p * Pow(a, m & 0x01);    // m % 2
                    default:
                        throw new ArgumentOutOfRangeException(nameof(n), $"べき指数{nameof(n)}は0以上の整数でなければなりません。");
                }
            }

            private static List<int> _factorialCache;
            private static List<int> FactorialCache => _factorialCache ??= new List<int>() { 1 };
            private static int[] FactorialInverseCache { get; set; }
            const int defaultMaxFactorial = 1000000;

            public static Modular Factorial(int n)
            {
                if (n < 0)
                {
                    throw new ArgumentOutOfRangeException(nameof(n), $"{nameof(n)}は0以上の整数でなければなりません。");
                }

                for (int i = FactorialCache.Count; i <= n; i++)  // Countが1（0!までキャッシュ済み）のとき1!～n!まで計算
                {
                    FactorialCache.Add((int)((long)FactorialCache[i - 1] * i % Mod));
                }
                return new Modular(FactorialCache[n]);
            }

            public static Modular Permutation(int n, int r)
            {
                CheckNR(n, r);
                return Factorial(n) / Factorial(n - r);
            }

            public static Modular Combination(int n, int r)
            {
                CheckNR(n, r);
                r = Math.Min(r, n - r);
                try
                {
                    return new Modular(FactorialCache[n]) * new Modular(FactorialInverseCache[r]) * new Modular(FactorialInverseCache[n - r]);
                }
                catch (Exception ex) when (ex is NullReferenceException || ex is ArgumentOutOfRangeException)
                {
                    throw new InvalidOperationException($"{nameof(Combination)}を呼び出す前に{nameof(InitializeCombinationTable)}により前計算を行う必要があります。", ex);
                }
            }

            public static void InitializeCombinationTable(int max = defaultMaxFactorial)
            {
                Factorial(max);
                FactorialInverseCache = new int[max + 1];

                var fInv = (Modular.One / Factorial(max)).Value;
                FactorialInverseCache[max] = fInv;
                for (int i = max - 1; i >= 0; i--)
                {
                    fInv = (int)((long)fInv * (i + 1) % Mod);
                    FactorialInverseCache[i] = fInv;
                }
            }

            public static Modular CombinationWithRepetition(int n, int r) => Combination(n + r - 1, r);

            private static void CheckNR(int n, int r)
            {
                if (n < 0)
                {
                    throw new ArgumentOutOfRangeException(nameof(n), $"{nameof(n)}は0以上の整数でなければなりません。");
                }
                if (r < 0)
                {
                    throw new ArgumentOutOfRangeException(nameof(r), $"{nameof(r)}は0以上の整数でなければなりません。");
                }
                if (n < r)
                {
                    throw new ArgumentOutOfRangeException($"{nameof(n)},{nameof(r)}", $"{nameof(r)}は{nameof(n)}以下でなければなりません。");
                }
            }

            public override string ToString() => $"{Value} (mod {Mod})";
            public override bool Equals(object obj) => obj is Modular m ? Equals(m) : false;
            public bool Equals([System.Diagnostics.CodeAnalysis.AllowNull] Modular other) => Value == other.Value;
            public int CompareTo([System.Diagnostics.CodeAnalysis.AllowNull] Modular other) => Value.CompareTo(other.Value);
            public override int GetHashCode() => Value.GetHashCode();
        }

    }
}

namespace YukicoderContest255
{
    class Program
    {
        static void Main(string[] args)
        {
            IAtCoderQuestion question = new QuestionB();
            var answers = question.Solve(Console.In);

            var writer = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            Console.SetOut(writer);
            foreach (var answer in answers)
            {
                Console.WriteLine(answer);
            }
            Console.Out.Flush();
        }
    }
}

#region Base Class

namespace YukicoderContest255.Questions
{

    public interface IAtCoderQuestion
    {
        IEnumerable<object> Solve(string input);
        IEnumerable<object> Solve(TextReader inputStream);
    }

    public abstract class AtCoderQuestionBase : IAtCoderQuestion
    {
        public IEnumerable<object> Solve(string input)
        {
            var stream = new MemoryStream(Encoding.Unicode.GetBytes(input));
            var reader = new StreamReader(stream, Encoding.Unicode);

            return Solve(reader);
        }

        public abstract IEnumerable<object> Solve(TextReader inputStream);
    }
}

#endregion

#region Extensions

namespace YukicoderContest255.Extensions
{
    public static class TextReaderExtensions
    {
        public static int ReadInt(this TextReader reader) => int.Parse(ReadString(reader));
        public static long ReadLong(this TextReader reader) => long.Parse(ReadString(reader));
        public static double ReadDouble(this TextReader reader) => double.Parse(ReadString(reader));
        public static string ReadString(this TextReader reader) => reader.ReadLine();

        public static int[] ReadIntArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(int.Parse).ToArray();
        public static long[] ReadLongArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(long.Parse).ToArray();
        public static double[] ReadDoubleArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(double.Parse).ToArray();
        public static string[] ReadStringArray(this TextReader reader, char separator = ' ') => reader.ReadLine().Split(separator);

        // Supports primitive type only.
        public static T1 ReadValue<T1>(this TextReader reader) => (T1)Convert.ChangeType(reader.ReadLine(), typeof(T1));

        public static (T1, T2) ReadValue<T1, T2>(this TextReader reader, char separator = ' ')
        {
            var inputs = ReadStringArray(reader, separator);
            var v1 = (T1)Convert.ChangeType(inputs[0], typeof(T1));
            var v2 = (T2)Convert.ChangeType(inputs[1], typeof(T2));
            return (v1, v2);
        }

        public static (T1, T2, T3) ReadValue<T1, T2, T3>(this TextReader reader, char separator = ' ')
        {
            var inputs = ReadStringArray(reader, separator);
            var v1 = (T1)Convert.ChangeType(inputs[0], typeof(T1));
            var v2 = (T2)Convert.ChangeType(inputs[1], typeof(T2));
            var v3 = (T3)Convert.ChangeType(inputs[2], typeof(T3));
            return (v1, v2, v3);
        }

        public static (T1, T2, T3, T4) ReadValue<T1, T2, T3, T4>(this TextReader reader, char separator = ' ')
        {
            var inputs = ReadStringArray(reader, separator);
            var v1 = (T1)Convert.ChangeType(inputs[0], typeof(T1));
            var v2 = (T2)Convert.ChangeType(inputs[1], typeof(T2));
            var v3 = (T3)Convert.ChangeType(inputs[2], typeof(T3));
            var v4 = (T4)Convert.ChangeType(inputs[3], typeof(T4));
            return (v1, v2, v3, v4);
        }

        public static (T1, T2, T3, T4, T5) ReadValue<T1, T2, T3, T4, T5>(this TextReader reader, char separator = ' ')
        {
            var inputs = ReadStringArray(reader, separator);
            var v1 = (T1)Convert.ChangeType(inputs[0], typeof(T1));
            var v2 = (T2)Convert.ChangeType(inputs[1], typeof(T2));
            var v3 = (T3)Convert.ChangeType(inputs[2], typeof(T3));
            var v4 = (T4)Convert.ChangeType(inputs[3], typeof(T4));
            var v5 = (T5)Convert.ChangeType(inputs[4], typeof(T5));
            return (v1, v2, v3, v4, v5);
        }

        public static (T1, T2, T3, T4, T5, T6) ReadValue<T1, T2, T3, T4, T5, T6>(this TextReader reader, char separator = ' ')
        {
            var inputs = ReadStringArray(reader, separator);
            var v1 = (T1)Convert.ChangeType(inputs[0], typeof(T1));
            var v2 = (T2)Convert.ChangeType(inputs[1], typeof(T2));
            var v3 = (T3)Convert.ChangeType(inputs[2], typeof(T3));
            var v4 = (T4)Convert.ChangeType(inputs[3], typeof(T4));
            var v5 = (T5)Convert.ChangeType(inputs[4], typeof(T5));
            var v6 = (T6)Convert.ChangeType(inputs[5], typeof(T6));
            return (v1, v2, v3, v4, v5, v6);
        }

        public static (T1, T2, T3, T4, T5, T6, T7) ReadValue<T1, T2, T3, T4, T5, T6, T7>(this TextReader reader, char separator = ' ')
        {
            var inputs = ReadStringArray(reader, separator);
            var v1 = (T1)Convert.ChangeType(inputs[0], typeof(T1));
            var v2 = (T2)Convert.ChangeType(inputs[1], typeof(T2));
            var v3 = (T3)Convert.ChangeType(inputs[2], typeof(T3));
            var v4 = (T4)Convert.ChangeType(inputs[3], typeof(T4));
            var v5 = (T5)Convert.ChangeType(inputs[4], typeof(T5));
            var v6 = (T6)Convert.ChangeType(inputs[5], typeof(T6));
            var v7 = (T7)Convert.ChangeType(inputs[6], typeof(T7));
            return (v1, v2, v3, v4, v5, v6, v7);
        }

        public static (T1, T2, T3, T4, T5, T6, T7, T8) ReadValue<T1, T2, T3, T4, T5, T6, T7, T8>(this TextReader reader, char separator = ' ')
        {
            var inputs = ReadStringArray(reader, separator);
            var v1 = (T1)Convert.ChangeType(inputs[0], typeof(T1));
            var v2 = (T2)Convert.ChangeType(inputs[1], typeof(T2));
            var v3 = (T3)Convert.ChangeType(inputs[2], typeof(T3));
            var v4 = (T4)Convert.ChangeType(inputs[3], typeof(T4));
            var v5 = (T5)Convert.ChangeType(inputs[4], typeof(T5));
            var v6 = (T6)Convert.ChangeType(inputs[5], typeof(T6));
            var v7 = (T7)Convert.ChangeType(inputs[6], typeof(T7));
            var v8 = (T8)Convert.ChangeType(inputs[7], typeof(T8));
            return (v1, v2, v3, v4, v5, v6, v7, v8);
        }
    }
}

#endregion