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

int main() {
    double princpial;
    int term;
    
    cin >> principal >> term;
    
    if (principal < 0) {
        cout << "Invalid input";
        return 0;
    }
    if (term < 1) {
        cout << -1;
        return 0;
    }
    
    double monthlyRate = 5.0 / (100 * 12);
    
    double intrest = principal * monthlyRate * term;
    
    cout << fixed << setprecision(2) << intrest;
    
    return 0;
}