#include <iostream>

using namespace std;

int main() {
    int n;
    cin >> n;
    int totalLikes = 0;
    int current = 5;
    for (int i=0; i<n; ++i) {
        totalLikes += current / 2;
        current = (current / 2) * 3;
    }
    cout << totalLikes << endl;
}