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


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


def div_num(s, n):
    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
    return dp[-1]



if s < 0:
     print(0)
else:
    print(div_num(s, n))