MOD = 10 ** 9 + 7
N, S, K = map(int, input().split())
S -= K * N * (N - 1) // 2
if S < 0:
    print(0)
    exit()
A = [0] * S + [1]
for i in reversed(range(2, N + 1)):
    for j in reversed(range(i, S + 1)):
        A[j - i] += A[j]
        A[j - 1] %= MOD
print(sum(A) % MOD)