ZJUT_1175

#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;
int main()
{
double q, n;
double sum;
cout.precision(3);
while(cin>>n>>q)
{
if(q==1) sum = 1+n;
else
sum = (1-pow(q,n+1))/(1-q);
cout<<fixed<<sum<<endl;
}
return 0;
}