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

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

DP = [[0 for _ in range(m + 1)] for _ in range(n + 1)]
DP[0][0] = 1
for i in range(1, n + 1):
    for j in range(m + 1):
        if j - i >= 0:
            DP[i][j] = (DP[i - 1][j] + DP[i][j - i]) % mod
        else:
            DP[i][j] = DP[i - 1][j]
print(DP[n][m])