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


s -= k * n * (n - 1) // 2
if s < 0:
    print(0)
    exit()

dp = [[0 for _ in range(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:
            dp[i][j] += dp[i][j-i]

        dp[i][j] %= mod

print(dp[n][s])