#include <iostream>
#include <algorithm>
using namespace std;
const int N = 1e4 + 10;
int n;

int main(){
    cin >> n;
    int res = n;
    while(n >= 3){
        res += n / 3;
        n = n % 3 + n / 3;
    }
    cout << res << endl;
    return 0;
}