#include <iostream>
#include <cstdio>
using namespace std;

int main()
{
    int n;
    scanf("%d", &n);
    int res = n, cap = n;
    while (cap >= 3)
    {
        res += cap / 3;
        cap = cap / 3 + cap % 3;
    }
    printf("%d", res);
    return 0;
}