N,S,K = map(int,input().split())
prev = (N**2-N)//2*K
mod = 10**9 + 7
DP = [[1 for j in range(S+1)] for i in range(N)]
for i in range(1,N):
  for j in range(S+1):
    if i < j:
      DP[i][j] = (DP[i][j-i-1] + DP[i-1][j])%mod
    else:
      DP[i][j] = DP[i-1][j]
#print(DP)
if prev > S:
  print('0')
else:
  print(DP[N-1][S-prev])