#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000

template <class S,
          S (*op0)(S, S),
          S (*e0)(),
		  S (*op1)(S, S),
          S (*e1)()
          >
struct matrix{
	vector<vector<S>> v;
	int _h,_w;
	
	matrix(vector<vector<S>> X){
		v = X;
		_h = X.size();
		_w = 0;
		if(X.size()>0)_w = X[0].size();
	}
	
	matrix(int h,int w){
		v.resize(h,vector<S>(w,e0()));
		_h = h;
		_w = w;
	}
	
	void add_element(int from,int to,S x){
		v[to][from] = op0(v[to][from],x);
	}
	
	matrix e(){
		assert(_h==_w);
		matrix<S,op0,e0,op1,e1> ret(_h,_w);
		for(int i=0;i<_h;i++){
			for(int j=0;j<_w;j++){
				if(i==j)ret.v[i][j] = e1();
				else ret.v[i][j] = e0();
			}
		}
		return ret;
	}
	
	matrix &operator*=(const matrix &another){
		matrix<S,op0,e0,op1,e1> ret(_h,another._w);
		for(int i=0;i<_h;i++){
			for(int j=0;j<another._w;j++){
				ret.v[i][j] = e0();
				for(int k=0;k<_w;k++){
					ret.v[i][j] = op0(ret.v[i][j],op1(v[i][k],another.v[k][j]));
				}
			}
		}

		v = ret.v;
		return (*this);
	}
	
	matrix operator*(const matrix &another)const{
		return (matrix(*this)*=another);
	}
	
	matrix pow(long long cnt){
		matrix<S,op0,e0,op1,e1> ret = e();
		auto temp = *this;
		while(cnt!=0LL){
			if((cnt&1)==1){
				ret *= temp;
			}
			temp *= temp;
			cnt>>=1;
		}
		return ret;
	}
};

long double op0(long double a,long double b){
	return a+b;
}

long double e0(){
	return 0;
}

long double op1(long double a,long double b){
	return a*b;
}

long double e1(){
	return 1;
}

int main(){
	
	int N;
	cin>>N;
	
	matrix<long double,op0,e0,op1,e1> M(2,2);
	M.add_element(0,1,1.0);
	M.add_element(0,0,19.0/4.0);
	M.add_element(1,0,-3.0);
	
	if(N==0){
		cout<<4.0<<endl;
		return 0;
	}
	matrix<long double,op0,e0,op1,e1> temp(2,1);
	temp.v[0][0] = 3.0;
	temp.v[1][0] = 4.0;
	
	temp = M.pow(N-1) * temp;
	
	
	cout<<fixed<<setprecision(15)<<temp.v[0][0]<<endl;
	
	return 0;
}