#include "bits/stdc++.h"

#define rep(i,n) for(int i = 0;i < n;i++)
#define REP(i,n,k) for(int i = n;i < k;i++)
#define P(p) cout << (p) << endl;
#define sP(p) cout << setprecision(15) << fixed << p << endl;
#define pi 3.1415926535
#define IINF 1e9
#define LINF 1e18
#define vi vector<int>
#define mp make_pair
#define max(a,b,c) max(a,max(b,c))
#define min(a,b,c) min(a,min(b,c))
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
int dx[] = { 0, 1, 0, -1 };
int dy[] = { -1, 0, 1, 0 };

unsigned long long sttoi(std::string str) {
    unsigned long long ret;
    std::stringstream ss; ss << str;
    ss >> ret;
    return ret;
}

ull gcd(ull a, ull b){
    if (b > a)swap(a, b);
    if (b == 0) return a;
    return gcd(b, a%b);
}

void solve() {
  int n;
  cin >> n;
  sP(4.0*pow(0.75,n));
}

int main() {
    solve();
    return 0;
}