mod = 10**9+7
n, k = map(int, input().split())
mod = 10**9+7
dp = [1]*(k+2)
tmp = [0]*(k+2)
for i in range(1, n+1):
    for j in range(k+1):
        dp[j+1] = (dp[j+1] + dp[j]) % mod
        tmp[j] = dp[j]
        if j-i+1 > 0:
            tmp[j] = (tmp[j] - dp[j-i]) % mod
    dp, tmp = tmp, dp
print(dp[k])