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