MOD = 10 ** 9 + 7

n, k = map(int, input().split())
ans = 0

def comb(n, k):
    if k > n or k < 0:
        return 0
    ret = 1
    k = min(k, n - k)
    for i in range(n, n - k, -1): ret *= i
    for i in range(1, k + 1): ret //= i
    return ret

a = 1
b = 1
nn = n + k - 1
rr = n
for i in range(nn, nn - rr, -1):
    b *= i
    b %= MOD
inv = 1
for i in range(1, rr + 1):
    inv *= i
    inv %= MOD
b *= pow(inv, MOD - 2, MOD)
b %= MOD

for i in range(n):
    ans += a * b
    ans %= MOD
    a *= (n - 1 - i) * pow(i + 1, MOD - 2, MOD) % MOD
    a %= MOD
    b *= pow(n + k - 1 - i, MOD - 2, MOD) * (k - 1 - i) % MOD
    b %= MOD
print(ans)