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