#include <cmath>
#include <iomanip>
#include <iostream>

using namespace std;

double get_price(int spent_money, int distance) {
    double price = 0;
    if (distance <= 6) {
        price = 3;
    } else {
        price = 4;
    }
    distance -= 12;
    if (distance > 0 && distance <= 32 - 12) { price += ceil(distance / 10.0); }
    distance -= 32 - 12;
    if (distance > 0) { price += ceil(distance / 20.0); }
    if (spent_money >= 400) { return price; }
    if (spent_money >= 150) { return price * 0.5; }
    if (spent_money >= 100) { return price * 0.8; }
    return price;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int spent_money, distance;
    cin >> spent_money >> distance;
    cout << fixed << setprecision(2) << get_price(spent_money, distance) << endl;


    return 0;
}