#include <iostream>
#include <cstdlib>
#include <cmath>
using namespace std;
double an(int x, int n)
{
	double sum;
	int i;
	sum=1/x;
	for (i=2; i<=n-1; i=i+2)
	{
		sum = sum + i/pow(x,i+1);
	}
	return (sum);
}

int main()
{
	int x,n;
	cout<<"DWSE x<>0:"<<endl;
	cin>>x;
	cout<<"DWSE n peritto:"<<endl;
	do{
		cin>>n;
	} while(n%2==0);
	cout<<an(x,n)<<endl;
	system("PAUSE");
	return 0;
}