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