N,S,K=map(int,input().split())
S=S-(K*N*(N-1)//2)+1
if S<=0:
  print(max(0,S+1))
  exit()
mod=10**9+7
DP=[[0]*(S+1) for i in range(N+1)]
DP[0][0]=1
k=0
for i in range(N):
  for j in range(S):
    k=j
    while k<=S:
      DP[i+1][k]=(DP[i+1][k]+DP[i][j])%mod
      k+=N-i
print(DP[-1][-1])