#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

using Vec = vector<long double>;
using Mat = vector<Vec>;

Mat Mul(const Mat& A, const Mat& B){
    Mat C(A.size(), Vec(B[0].size()));
    for(int i = 0; i < (int)A.size(); ++i){
        for(int k = 0; k < (int)A[0].size(); ++k){
            for(int j = 0; j < (int)B.size(); ++j){
                C[i][j] += A[i][k] * B[k][j];
            }
        }
    }
    return C;
}

Mat Pow(Mat A, int n){
    Mat B(A.size(), Vec(A.size()));
    for(int i = 0; i < (int)A.size(); ++i)  B[i][i] = 1;
    while(n > 0){
        if(n & 1)   B = Mul(B, A);
        A = Mul(A, A);
        n >>= 1;
    }
    return B;
}

long double A[105];

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N;
    cin >> N;
    cout << fixed << setprecision(15);
    A[0] = 4; A[1] = 3;
    for(int i = 2; i <= N; ++i){
        A[i] = (19 * A[i - 1] - 12 * A[i - 2]) / 4;
    }
    cout << A[N] << endl;

    return 0;
}