N, S, K = map(int, input().split())
mod = 10 ** 9 + 7
S -= K * N * (N - 1) // 2
if S < 0:
    print(0)
    exit()
elif S == 0:
    print(1)
    exit()
    
dp = [[0] * (N+5) for _ in range(S+5)]
for i in range(1, S + 1):
    dp[i][1] = 1
    if i <= N + 4:
        dp[i][i] = 1
    for j in range(2, min(i, N+1)):
        dp[i][j] = dp[i-1][j-1]
        if i > j:
            dp[i][j] += dp[i-j][j]
        dp[i][j] %= mod
        
print(sum(dp[S][:N+1])%mod)