MOD = 10 ** 9 + 7
N, S, K = map(int, input().split())

S -= K * N * (N - 1) // 2
if S < 0:
    print(0)
    exit()

dp = [0] * (S + 1)
dp[0] = 1
for i in range(N):
    for j in range(N - i, S + 1):
        dp[j] = (dp[j] + dp[j - (N - i)]) % MOD
print(dp[S])