import java.io.*;
import java.util.*;
//https://pastebin.com/uSuh7zuG
public class DPM_1 {
	//memo[i][j]   i children and j candies store the numbers of ways
	//memo[i][0]   1
	//memo[i][j] = memo[i-1][j]+memo[i-1][j-1]+memo[i-1][j-2]+...+memo[i-1][j-ai];
	public static long memo[][] = new long[2][1000005];
	public static long prefixSum[][] = new long[2][1000005];
	public static int a[] = new int[100005];
	public static final long MOD = 1000000007;

	public static void main(String[] args) throws IOException
	{
		BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
		String[] tmp = in.readLine().split(" ");
		int N = Integer.parseInt(tmp[0]);
		int K = Integer.parseInt(tmp[1]);

		tmp = in.readLine().split(" ");
		for (int i = 1; i <= N; i++)
			a[i] = Integer.parseInt(tmp[i-1]);

		memo[0][0] = 1;
		int cur = 1, prev = 0;
		for (int i = 1; i <= N; i++)
		{
			for (int j = 0; j <= K; j++)
			{
				//Using prefixSum to calculate current value
				memo[cur][j] = memo[prev][j];
				if (j-a[i] > 0)
				memo[cur][j] = memo[prev][j]-memo[prev][j-a[i]-1];
				memo[cur][j] %= MOD;
				memo[cur][j] += MOD;
				memo[cur][j] %= MOD;
			}
			//recalculate prefix sum
			for (int j = 1; j <= K; j++)
				memo[cur][j] = (memo[cur][j] + memo[cur][j-1]) % MOD;
			cur ^= 1;
			prev ^= 1;
		}
		System.out.println(memo[prev][K]);
	}
}