k,n,d=gets.split(" ").map{|e| e.to_i}
k.times{|i|
	n-=d*i
}
if n<0 then
	puts 0
else
	m=10**9+7
	dp=Array.new(n+1,0)
	dp[0]=1
	(k-1).downto(1){|i|
		0.upto(n-i){|p1|
			dp[p1+i]=(dp[p1+i]+dp[p1])%m
		}
	}
	ans=0
	t=n
	while t>=0 do
		ans+=dp[t]
		t-=k
	end
	puts ans%m
end