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

base = sum(i * K for i in range(N))
if base > S:
    print(0)
    exit()
S -= base


# dp[i][j]  jをi分割
dp = [[0] * (S + 1) for _ in range(N + 1)]
dp[0][0] = 1
for i in range(1, N + 1):
    for j in range(S + 1):
        if j >= i:
            dp[i][j] = (dp[i - 1][j] + dp[i][j - i]) % mod
        else:
            dp[i][j] = dp[i - 1][j]

print(dp[N][S])