MOD = 10**9 + 7

N, S, K = map(int, input().split())

# Calculate the adjusted target sum T
T = S - K * N * (N - 1) // 2

if T < 0:
    print(0)
else:
    dp = [0] * (T + 1)
    dp[0] = 1
    # Iterate over each "coin" from N down to 1
    for coin in range(N, 0, -1):
        for t in range(coin, T + 1):
            dp[t] = (dp[t] + dp[t - coin]) % MOD
    print(dp[T] % MOD)