import java.util.*;

public class Main {
    private static final int M =  1000000007;

    private static long solve(int N, int K, int[] a) {
        int[] ways = new int[K+1];
        int[] diff = new int[K+1];
        ways[0] = 1;

        for (int ai: a) {
            Arrays.fill(diff, 0);

            int s = 0;
            for (int i = 1; i <= K; i++) {
                int add = ways[i-1];
                int remove = (i-ai-1 >= 0) ? ways[i-ai-1]: 0;
                s = (s + add - remove) % M;

                diff[i] = (diff[i] + s) % M;
            }

            for (int i = 0; i <= K; i++)
                ways[i] = (ways[i] + diff[i]) % M;
        }

        return ways[K];
    }

    public static long run(Scanner scanner) {
        int N = scanner.nextInt();
        int K = scanner.nextInt();
        int[] a = new int[N];
        for (int i=0; i < N; i++) a[i] = scanner.nextInt();

        return solve(N, K, a);
    }

    public static void main(String[] args) {
        try (Scanner scanner = new Scanner(System.in)) {
            System.out.println(run(scanner));
        }
        Tests.run();
    }
}

class Tests {
    public static void run() {
        testCase("3 4\n" +
                "1 2 3", 5);
        testCase("1 10\n" +
                "9", 0);
        testCase("2 0\n" +
                "0 0", 1);
        testCase("4 100000\n" +
                "100000 100000 100000 100000", 665683269);

        System.out.println("DONE");
    }

    private static void testCase(String input, long expected) {
        try (Scanner scanner = new Scanner(input)) {
            long result = Main.run(scanner);
            if (result != expected) System.out.println("TEST FAILED: was " + result + " expected " + expected + " on input\n" + input);
        }
    }
}