#include<iostream>
#include<iomanip>
using namespace std;
int main(){
    double principal;
    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 interest =principal *monthlyRate*term;
    cout<<fixed<<setpercision(2)<< interest;
    return 0;
}