
import java.io.BufferedReader;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Scanner;
import java.util.StringTokenizer;

public class Solution{
	static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) throws Exception {
		int n = sc.nextInt();
		int k =sc.nextInt();
		int[] arr = input(n);
		
		long[] dp = new long[k+1];
		long[] cum = new long[k+1];
		for(int i = 0 ; i < n;i++ ) {
			dp= new long[k+1];
			long mod = 1000000007;
			for(int j = 0 ;j <= k ;j++) {
				if(i==0) {
					if(j<=arr[i])
					dp[j]=1;
					continue;
				}
				dp[j] = cum[j];
				dp[j]-= (j - arr[i]>0)? dp[j - arr[i]-1] : 0 ;
				dp[j]%=mod;
			}
			cum = new long[k+1];
			
			for(int j = 0 ;j <= k ;j++) {
				cum[j] = dp[j];
				cum[j]+= (j>0 ? cum[j-1] : 0);
				
				cum[j] %=mod;
			}
			
		}
	
		System.out.println(dp[k]);
	}

	public static int[] input(int n) throws Exception {

		int[] arr = new int[n];
		for (int i = 0; i < n; i++) {
			arr[i] = sc.nextInt();
		}
		return arr;
	}

	public static int[][] input(int n, int m) throws Exception {

		int[][] arr = new int[n][m];
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < m; j++) {

				arr[i][j] = sc.nextInt();
			}
		}
		return arr;
	}

}
