def pnk(S,N):
  mod = 10**9+7
  dp = [ [1]*(S+1) for _ in range(N+1) ]
  for i in range(2, N+1):
    for j in range(S+1):
      if j >= i:
        dp[i][j] = (dp[i-1][j]+dp[i][j-i]) % mod
      else:
        dp[i][j] = dp[i-1][j] % mod

  return dp[-1][-1]

N,S,K = map(int,input().split())
S = S - (N*(N-1)//2)*K
if S < 0:
  print(0)
else:
  print(pnk(S,N))