#!/usr/bin/ruby
Mod=10**9+7
def count(i,d)
	(d+1).pow(i)-1
end

def sum(i,d)
	((d+1)*((d+1).pow(i)-1)%Mod*d.pow(Mod-2,Mod)%Mod-i+Mod)%Mod
end
def sum_n(i,d,n)
	return 0 if n==0
	s=count(i-1,d)
	t=n/(1+s)
	(t*(i+sum(i-1,d))%Mod+sum_n(i-1,d,n-t*(1+s)))%Mod
end
n,b,d=`dd`.split.map &:to_i
i=1
loop{
	if count(i,d)>n
		p (sum(b,d)+Mod-sum_n(i,d,n))%Mod
		exit
	end
	i+=1
}