def div_ceil (l, r)
	q = l / r ; q += 1 if l % r != 0 ; q
end

def binpow (x)
	if x == 0 then
		1
	else
		lowest = ((x % 2 == 0) ? 1 : $kd)

		lowest * (binpow(x / 2) ** 2)
	end
end

def calc (n)
	($a - 1) * binpow(n) + (binpow(n + 1) - 1) / $k
end

def init_r
	maybe = 1
	maybe *= 2 while calc(maybe) < $m
	maybe
end

def solve
	if $k == 0 then
		return $m - $a
	end
	$kd = $k + 1
	l = 0
	r = init_r

	while l != r
		if calc((l + r) / 2) < $m then
			l = div_ceil(l + r, 2)
		else
			r = (l + r) / 2
		end
	end

	l
end

$m     = gets.chomp.to_i(10)
$a, $k = gets.chomp.split(' ').map{|e| e.to_i(10)}

puts solve