N, S, K = [int(x) for x in input().split()]
mod = 10**9 + 7

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

if M < 0:
    print(0)
    exit()

dp = [[0]*(M + 1) for _ in range(N + 1)]
dp[0][0] = 1

for i in range(1, N + 1):
    for j in range(M + 1):
        if j - i >= 0:
            dp[i][j] = (dp[i - 1][j] + dp[i][j - i]) % mod
        else:
            dp[i][j] = dp[i - 1][j]

print(dp[N][M])