def solve():
    m = 10 ** 9 + 7
    N, S, K = map(int, input().split())
    
    S -= K * N * (N - 1) // 2
    
    if S < 0:
        print(0)
        return
    
    S += 1
    dp = [1] * S
    
    for i in range(2, N + 1):
        for j in range(i, S):
            dp[j] = (dp[j] + dp[j-i]) % m
    
    print(dp[-1])

solve()