N,S,K=map(int,input().split())
S-=N*(N-1)*K//2
if S<0:print(0)
else:
  dp=[1]*(S+1)
  for n in range(2,N):
    for s in range(n,S+1): dp[s]+=dp[s-n]
  print(sum(dp[S::-N])%(10**9+7))