#include<iostream>
#include<iomanip>
using namespace std ;
int main(){
    try{
    int num,d;
    if(d==0){
        throw "-1"
    }
    else{
        cout<<fixed<<setprecision(2)<<num*d;
    }
    }
    catch(const char* msg){
        cout<<msg;
    }
    return 0;
}