N, K = map(int, input().split())
dp = [[0]*(K+1) for _ in range(N+1)]
dp[1][0] = 1
MOD = 10**9+7

for i in range(2, N+1):
    for j in range(K+1):
        for k in range(i):
            if j-k<0:
                break
            
            dp[i][j] += dp[i-1][j-k]
            dp[i][j] %= MOD

print(sum(dp[N][:K+1])%MOD)