def create_multi_list(init_val, *args):
    if len(args) == 1:
        return [init_val] * args[0]
    else:
        return [create_multi_list(init_val, *args[1:]) for _ in range(args[0])]

n, s, k = map(int, input().split())
mod = 10 ** 9 + 7
s = s - k * n * (n-1) // 2
if s < 0:
    print(0)
    quit()
dp = create_multi_list(0, s+1, n+1)
dp[0][0] = 1
for i in range(s+1):
    for j in range(n+1):
        if i >= j:
            dp[i][j] = (dp[i][j-1] + dp[i-j][j]) % mod
        else:
            dp[i][j] = dp[i][j-1]
print(dp[-1][-1])