import sys

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

class mint:
    def __init__(self, x):
        self.__x = x % md

    def __repr__(self):
        return str(self.__x)

    def __neg__(self):
        return mint(-self.__x)

    def __add__(self, other):
        if isinstance(other, mint): other = other.__x
        return mint(self.__x + other)

    def __sub__(self, other):
        if isinstance(other, mint): other = other.__x
        return mint(self.__x - other)

    def __rsub__(self, other):
        return mint(other - self.__x)

    def __mul__(self, other):
        if isinstance(other, mint): other = other.__x
        return mint(self.__x * other)

    __radd__ = __add__
    __rmul__ = __mul__

    def __truediv__(self, other):
        if isinstance(other, mint): other = other.__x
        return mint(self.__x * pow(other, md - 2, md))

    def __rtruediv__(self, other):
        return mint(other * pow(self.__x, md - 2, md))

    def __pow__(self, power, modulo=None):
        return mint(pow(self.__x, power, md))

md=10**9+7

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

main()