n,s,k = map(int, input().split())
mod = 10**9+7
s -= (n*(n-1)//2)*k
if s <= 0:
  print(0)
  exit()

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

print(dp[-1][-1])