P = 10**9 + 7

N, S, K = map(int, input().split())
S -= N*(N - 1)*K // 2
if S < 0:
    print(0)
    exit()
dp = [[0]*(N + 1) for _ in range(S + 1)]
dp[0][0] = 1
for s in range(S + 1):
    for n in range(1, N + 1):
        if s >= n:
            dp[s][n] = (dp[s][n - 1] + dp[s - n][n]) % P
        else:
            dp[s][n] = dp[s][n - 1]
ans = dp[S][N]
print(ans)