#include<iostream>

int main() {
	long long n, g, v;

	std::cin >> n >> g >> v;

	long long gareki = g * (n / 5);

	long long seisu = static_cast<long long>(gareki / v);

	gareki -= seisu * v;

	long long syousu = 1000000000000LL * gareki / v;

	std::cout << seisu << '.' << syousu << std::endl;
	return 0;
}