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

sp = s - (n * (n - 1) // 2) * k

if sp < 0:
    print(0)
    exit()

dp = [[0] * (sp + 1) for _ in range(n + 1)]
dp[0][0] = 1

for i in range(1, n + 1):
    for j in range(sp + 1):
        if j - i >= 0:
            dp[i][j] = dp[i][j-i] + dp[i-1][j]
        else:
            dp[i][j] = dp[i-1][j]

        dp[i][j] %= mod

ans = dp[n][sp]
print(ans)