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

s = s - (n-1)*n//2 * k
if s < 0:
    print("{}".format(0))
    exit()

dp = [[0 for i in range(s+1)] for i in range(n+1)]
dp[0][0] = 1

for i in range(n):
    for j in range(s+1):
        kari = n-i
        if j >= kari:
            dp[i+1][j] = (dp[i][j] + dp[i+1][j-kari]) % p
        else:
            dp[i+1][j] = dp[i][j]

ans = dp[n][s]
print("{}".format(ans))