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):
    acc = [0]
    
    for j in range(K+1):
        acc.append((acc[-1]+dp[i-1][j])%MOD)
    
    for j in range(K+1):
        dp[i][j] = (acc[j+1]-acc[max(0, j-(i-1))])%MOD

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