import sys

sys.setrecursionlimit(10 ** 6)

def MI(): return map(int, sys.stdin.readline().split())

def main():
    md = 10 ** 9 + 7
    n,k=MI()
    MI()
    dp=[[0]*(k+1) for _ in range(n+1)]
    dp[0][0]=1
    for i in range(n):
        s=0
        w=n-i
        for j in range(k+1):
            s+=dp[i][j]
            if j-w>=0:s-=dp[i][j-w]
            s%=md
            dp[i+1][j]=s
    print(sum(dp[n])%md)

main()