def solve():
    MOD = 10 ** 9 + 7

    N, S, K = list(map(int, input().split()))
    S -= K * N * (N - 1) // 2

    if S < 0:
        print(0)
        return

    dp = [[0 for s in range(20101)] for i in range(N + 1)]
    dp[0][0] = 1

    for i in range(1, N + 1):
        for j in range(S + 1):
            dp[i][j] = dp[i - 1][j] + dp[i][j - (N - i + 1)]
            if dp[i][j] > MOD:
                dp[i][j] -= MOD

    print(dp[N][S])


if __name__ == '__main__':
    solve()