using System;
using System.Diagnostics.SymbolStore;
using System.IO;

namespace Contest
{
    class Program
    {
        private Scanner sc;

        private long[,] dp;
        private int N;
        private int K;
        private int[] A;
        private long Mod = 1000000007;

        public void Solve()
        {
            sc = new Scanner();
            N = sc.NextInt();
            K = sc.NextInt();
            A = sc.IntArray();

            dp = new long[N + 1, K + 1];
            dp[0, 0] = 1;
            int b = 0;
            for (int i = 0; i < N; i++)
            {
                long sum = 0;
                for (int j = 0; j <= Math.Min(K, A[i] + b); j++)
                {
                    // dp[i+1,j] = dp[i,j-A[i]] ~ dp[i,j]の和
                    if (j - A[i] - 1 >= 0)
                    {
                        sum -= dp[i, j - A[i] - 1];
                    }

                    sum += dp[i, j];

                    sum %= Mod;
                    if (sum < 0) sum += Mod;
                    dp[i + 1, j] = sum;
                }
                b += A[i];
            }

            //for (int i = 0; i <= N; i++)
            //{
            //    for (int j = 0; j <= K; j++)
            //    {
            //        Console.Write(dp[i, j]);
            //        Console.Write(" ");
            //    }
            //    Console.WriteLine();
            //}
            Console.WriteLine(dp[N, K]);
        }




        static void Main() => new Program().Solve();
    }
}

class Scanner
{
    public Scanner()
    {
        _stream = new StreamReader(Console.OpenStandardInput());
        _pos = 0;
        _line = new string[0];
        _separator = ' ';
    }
    private readonly char _separator;
    private readonly StreamReader _stream;
    private int _pos;
    private string[] _line;
    #region get a element
    public string Next()
    {
        if (_pos >= _line.Length)
        {
            _line = _stream.ReadLine().Split(_separator);
            _pos = 0;
        }
        return _line[_pos++];
    }
    public int NextInt()
    {
        return int.Parse(Next());
    }
    public long NextLong()
    {
        return long.Parse(Next());
    }
    public double NextDouble()
    {
        return double.Parse(Next());
    }
    #endregion
    #region convert array
    private int[] ToIntArray(string[] array)
    {
        var result = new int[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = int.Parse(array[i]);
        }

        return result;
    }
    private long[] ToLongArray(string[] array)
    {
        var result = new long[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = long.Parse(array[i]);
        }

        return result;
    }
    private double[] ToDoubleArray(string[] array)
    {
        var result = new double[array.Length];
        for (int i = 0; i < array.Length; i++)
        {
            result[i] = double.Parse(array[i]);
        }

        return result;
    }
    #endregion
    #region get array
    public string[] Array()
    {
        if (_pos >= _line.Length)
            _line = _stream.ReadLine().Split(_separator);
        _pos = _line.Length;
        return _line;
    }
    public int[] IntArray()
    {
        return ToIntArray(Array());
    }
    public long[] LongArray()
    {
        return ToLongArray(Array());
    }
    public double[] DoubleArray()
    {
        return ToDoubleArray(Array());
    }
    #endregion
}

Measured memory_bytes: 89056