# coding: utf-8

from itertools import accumulate as accum
import sys
input = sys.stdin.readline

def f(n, k, ai):
    mod = int(1e9 + 7)
    dp = [0] * (k + 1)
    dp[0] = 1
    for a in ai:
        # csum: Cumulative sum
        # dp[j] = dp[0] + dp[1] + ... + dp[j]
        # dp = list(accum(dp, lambda x, y: (x + y) % mod))
        dp = list(accum(dp))
        # j = 0 ～ a[i] までは累積和の結果そのままで a[i] + 1 以降は
        # dp[j] -= dp[j] - dp[j - a[i] - 1]
        dp[a + 1:] = [x - y for x, y in zip(dp[a + 1:], dp)]
        dp = [x % mod for x in dp]
    return(dp[k])

n, k = map(int, input().split()) # 1 <= n <= 100, 0 <= k <= 10^5
a = list(map(int, input().split()))
print(f(n, k, a))
