using System;
using System.Linq;
using System.Collections.Generic;
using static System.Console;
using System.Text;
using System.IO;
using static System.Math;
namespace AtCoder
{
    class Program
    {
        static public int[] Sarray() { return ReadLine().Split().Select(int.Parse).ToArray(); }
        static public List<int> Slist() { return ReadLine().Split().Select(int.Parse).ToList(); }

        static int[] A;
        static long[,] dp;
        static readonly long Mod = 1000000000 + 7;
        static void Main(string[] args)
        {
            var NK = Sarray();
            var N = NK[0];
            var K = NK[1];
            A = Sarray();
            var amax = A.Max();
            if(A.Sum()<K)
            {
                WriteLine(0);
                return;
            }
            dp = new long[N, K + 1];
            for (var i = 1; i < N; ++i)
                dp[i, 0] = 1;
            for (var i = 0; i <= A[0]; ++i)
                dp[0, i] = 1;
            var sum = A[0];
            for (var i = 1; i < N; ++i)
            {
                sum = Min(sum + A[i], K);
                for (var j = 1; j <= sum; ++j)
                {
                    dp[i, j] = dp[i - 1, j] + dp[i, j - 1];
                    if (0 < j - A[i])
                        dp[i, j] -= dp[i - 1, j - A[i] - 1];
                    dp[i, j] %= Mod;
                }
            }
            WriteLine(dp[N - 1, K]);
        }
    }
}