N, S, K = map(int, input().split())
MOD = 10 ** 9 + 7
for i in range(N):  # あらかじめK円ずつ増える分を差し引く
    S -= K * i
if S < 0:
    print(0)
    exit()
dp = [[0] * (S + 1) for _ in range(N + 1)]
dp[0][0] = 1  # dp[i][j] = jをi分割した時の総数
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]) % MOD
        else:
            dp[i][j] = dp[i - 1][j]
print(dp[N][S])