MOD = 10**9+7
n,k = map(int,input().split())
a = [1]
for i in range(n):
    a += [0]*i
    for j in range(i+1,len(a))[::-1]:
        a[j] -= a[j-i-1]
    for j in range(1,len(a)):
        a[j] += a[j-1]
        a[j] %= MOD
print(sum(a[:k+1])%MOD)