N,S,K = map(int,input().split())
S -= (K+(N-1)*K)*(N-1)//2
mod = 10**9 +7
if S == 0:
    print(1)
elif S < 0:
    print(0)
else:
    #dp[i][j]->i人でjを値の組み合わせの重複なしで分割するパターン数
    dp = [[0]*(S+1) for _ in range(N+1)]
    for i in range(N+1):
        dp[i][0]=1
    for j in range(S+1):
        dp[1][j] = 1
    for i in range(2,N+1):
        for j in range(1,S+1):
            dp[i][j] += dp[i-1][j]
            if j-i>=0:
                dp[i][j] += dp[i][j-i]

print(dp[-1][-1]%mod)