#include <iostream> #include <cstdio> #include <vector> #include <algorithm> #include <utility> #include <cmath> using namespace std; int main() { int n; cin >> n; // 漸化式をとくと Ak = 4 * (3/ 4)^k printf("%.50f\n", 4.0 * pow(0.75, n)); return 0; }