#include <iostream>

using namespace std;

int main() {
    double priceOver20kg, bagWeight;
    cin >> priceOver20kg >> bagWeight;

    int dayBefore, bagCount;
    cin >> dayBefore >> bagCount;

    if (bagWeight < 10) {
        priceOver20kg /= 5;
    }
    else if (bagWeight <= 20) {
        priceOver20kg /= 2;
    }

    if (dayBefore < 7) {
        priceOver20kg *= 1.4;
    }
    else if (dayBefore <= 30) {
        priceOver20kg *= 1.15;
    }
    else if (dayBefore > 30) {
        priceOver20kg *= 1.1;
    }

    double total = priceOver20kg * bagCount;

    printf("The total price of bags is: %.2f lv.\n", total);

    return 0;
}