N, S, K = map(int,input().split())
S -= N * ~-N * K // 2 - 1
if S < 1: print(0)
else:
  D = [1] * S
  for n in range(2, N):
    for s in range(n, S): D[s] += D[s - n]
  print(sum(D[S - 1::-N]) % (10 ** 9 + 7))