MOD = 10 ** 9 + 7

n, k = map(int, input().split())

dp = [0] * (k + 1)
dp[0] = 1
for i in range(n):
    dp2 = [0] * (k + 1)
    for j in range(1, k + 1):
        dp[j] += dp[j - 1]
        dp[j] %= MOD
    for j in range(k, -1, -1):
        if j >= i + 1:
            dp2[j] = dp[j] - dp[j - i - 1]
            dp2[j] %= MOD
        else:
            dp2[j] = dp[j] 
    dp = dp2
    
print(sum(dp) % MOD)