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();

        // Validation
        if (principal < 0) {
            System.out.println("Invalid input");
            return;
        }
        if (months < 1) {
            System.out.println("-1");
            return;
        }

        // Rate of interest = 5%
        double rate = 0.05;

        // Interest formula: P × R × T
        // T is in years, so months / 12.0
        double time = months / 12.0;
        double interest = principal * rate * time;

        System.out.printf("%.2f%n", interest);
    }
}