N,S,K=gets.split.map &:to_i
n=S-~-N*N*K/2
c=0
1.upto(N){|k|
  t=[1]*n
  2.upto(k){|i|i.upto(n-k){|j|t[j]+=t[j-i]}}
  c=(c+t[n-k])%1000000007
}if n>=0
p c