MOD = 10 ** 9 + 7

n, s, k = map(int, input().split())
s -= n * (k * (n - 1)) // 2
if s < 0:
    print(0)
    exit()
dp = [0] * (s + 1)
dp[0] = 1
for i in range(1, n + 1):
    for j in range(i, s + 1):
        dp[j] += dp[j - i]
        dp[j] %= MOD
print(dp[s])