

//12;03
import java.util.Scanner;

public class Main {

	private static Scanner in;
	private static int n;
	private static int[] a;
	private static int k;
	private static int[] dp;
	private static final int MOD = (int)1e9+7;
	
	public static void main(String[] args) {
		in = new Scanner(System.in);
		n = in.nextInt();
		k = in.nextInt();
		a = new int[n];
		for(int i=0; i<n; i++) a[i] = in.nextInt();
		dp = new int[k+1];
		dp[0] = 1;
		
		for(int i=n-1; i>=0; i--) {
			int[] pre = new int[k+1];
			pre[0] = dp[0];
			for(int j=1; j<k+1; j++) {
				pre[j] = (pre[j-1]+dp[j])%MOD;
			}
			
			for(int kLeft=k; kLeft>=0; kLeft--) {
				// dp[kLeft] is the sum of dp[kLeft] to dp[kLeft-a[i]]
				dp[kLeft] = ((pre[kLeft]-(kLeft-a[i]-1>=0?pre[kLeft-a[i]-1]:0))%MOD+MOD)%MOD;
			}
		}
		System.out.println(dp[k]);
		
	}

}
