def solve(N, S):
    mod = 10**9 + 7
    if S < 0: return 0
    elif S == 0: return 1
    dp = [1] * (S + 1)
    for n in range(2, N):
        for s in range(n, S + 1):
            dp[s] = (dp[s - n] + dp[s]) % mod
    return sum(dp[S::-N]) % mod    

N, S, K = map(int, input().split())
S -= N * (N-1) * K // 2
print(solve(N, S))