n, k = map(int, input().split())
a = list(map(int, input().split()))

cs_a, cnt = [0] * n, 0
for i in range(n):
    cnt += a[i]
    cs_a[i] = cnt

dp = [[0] * (n + 1) for i in range(k + 1)]

for i in range(k + 1):
    for j in range(1, n + 1):
        if i > cs_a[j - 1]:
            dp[i][j] = 0
        elif i == 0:
            dp[i][j] = 1
        elif i == 1:
            dp[i][j] = dp[i][j - 1] + min(1, a[j - 1])
        else:
            dp[i][j] = sum(dp[i - x][j - 1] for x in range(a[j - 1] + 1))

print(dp[k][n] % (10 ** 9 + 7))
