import java.util.Scanner;

public class LoanInterestCalculator {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int principal = sc.nextInt();
        int months = sc.nextInt();

        if (principal <= 0) {
            System.out.println("Invalid input");
            return;
        } else if (months <= 0) {
            System.out.println("-1");
            return;
        } else {
            double annualRate = 0.05;
            double monthlyRate = annualRate / 12;
            double interest = principal * monthlyRate * months;
            System.out.printf("%.2f\n", interest);
            return;
        }

        sc.close();
    }
}