M=10**9+7
n,s,k=map(int,input().split())
s-=n*(n-1)//2*k-1
if s<1:exit(print(0))
dp=[1]*s
for i in range(2,n+1):
 for j in range(i,s):dp[j]=(dp[j]+dp[j-i])%M
print(dp[-1])