N, S, K = map(int, input().split())
MOD = 10 ** 9 + 7

S -= N * ((N - 1) * K) // 2

def div_num(S, N):
    dp = [1] * (S + 1)
    for i in range(2, N + 1):
        for j in range(i, S + 1):
            dp[j] = (dp[j] + dp[j - 1]) % MOD
    return dp[-1]

if S < 0:
    print(0)
else:
    print(div_num(S, N))