#include <iostream>
#include <cmath>
using namespace std;

int main() {
	long long N, P;
	cin >> N >> P;
	double h, l, d, lenta, price;
	h = (1+N)*N*0.5;
	l = 0.5 + N*0.5;
	d = sqrt(h*h + l*l);
	lenta = ceil(d + d + 1);
	price = lenta * P;
	if (price >= 1000) {
		price *= 85;
	}
	else if (price >= 100) {
		price *= 90;
	}
	else {
		price *=100;
	}
	if (ceil(100./P) > lenta and price > 90*ceil(100./P)*P){
		price = 90*ceil(100./P)*P;
	}
	else if (ceil(1000./P) > lenta and price > 85*ceil(1000./P)*P) {
		price = 85*ceil(1000./P)*P;
	}
	cout << price;
}