n, k = map(int, input().split())
a = list(map(int, input().split()))
mod = 10**9+7
dp = {}
def rec(n, k):
    if k < 0:
        return 0
    if n == 0:
        return 1
    if (n,k) in dp:
        return dp[n,k]
    res = 0
    for i in range(n):
        res += rec(n-1, k-i)
        res %= mod
    dp[n,k] = res
    return res
print(rec(n, k))