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

solve()