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