n, s, k = map(int, input().split())
# 0 + k * (n - 1)
# k * n * (n - 1) // 2
s -= k * n * (n - 1) // 2
if s < 0:
    print(0)
    exit()
mod = 10 ** 9 + 7
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):
        dp[i][j] = dp[i - 1][j]
        if j - i >= 0:
            dp[i][j] += dp[i][j - i]
            if dp[i][j] >= mod:
                dp[i][j] -= mod
print(dp[n][s])