n, s, k = map(int, input().split())
mod = 10 ** 9 + 7

s -= n * ((n-1) * k) // 2

dp = (s + 1) * [1]
for i in range(2, n + 1):
    for j in range(i, s + 1):
        dp[j] = (dp[j] + dp[j - i]) % mod

if s < 0:
     print(0)
else:
    print(dp[-1])