#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

class Rational {
    ll gcd_(ll num1, ll num2){ return num2 == 0 ? num1: gcd_(num2, num1 % num2); }
    void norm(){ ll gcd = gcd_(num, den); num /= gcd, den /= gcd; }
public:
    ll num, den;
    Rational(ll n=0, ll d=1):num(n),den(d) { norm(); }
    const Rational operator+(const Rational &p)const{
        Rational ret(num*p.den+p.num*den,den*p.den);ret.norm();return ret;}
    const Rational operator-(const Rational &p)const{
        Rational ret(num*p.den-p.num*den,den*p.den);ret.norm();return ret;}
    const Rational operator-(void)const{
        Rational ret(-num,den);ret.norm();return ret;}
    const Rational operator*(const Rational &p)const{
        Rational ret(num*p.num, den*p.den);ret.norm();return ret;}
    const Rational operator/(const Rational &p)const{
        Rational ret(num*p.den, den*p.num);ret.norm();return ret;}
    bool operator==(const Rational &p)const{return (num==p.num && den==p.den);}
    bool operator< (const Rational &p)const{return (num*p.den<p.num*den);}
    operator ll(){return num/den;}
    operator double(){return (double)num/den;}
};
//static bool operator< (const Rational &p1, const Rational &p2){return (p1.num*p2.den<p2.num*p1.den);}
ostream &operator<<(ostream &os, const Rational &p){return(os<<p.num<<"/"<<p.den);}

int main(){
    int N;
    cin >> N;

    Rational a[2];
    a[0] = Rational(4);
    a[1] = Rational(3);
    if(N < 2){
        printf("%.16Lf\n", (long double)a[N].num/a[N].den);
        return 0;
    }

    for(int i = 2; i <= N; i++){
        Rational aa = a[1]*Rational(19,4) - a[0]*Rational(3);
        a[0] = a[1];
        a[1] = aa;
    }
    printf("%.16Lf\n", (long double)a[1].num/a[1].den);
}