#include "bits/stdc++.h"
using namespace std;

typedef long long Int;
#define REP(i,n) for(int (i)=0;(i)<(int)(n);++(i))

int main() {
	int n; cin >> n;
	double ans = 4;
	REP(i, n) ans = ans * 3 / 4;
	printf("%.12f\n", ans);
}