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

int main()
{
    int n,a,b;
    cin>>n;
    int res=n;
    while (n>=3){
        a=n/3;
        res += a;
        b=n%3;
        n=a+b;

    }
    printf("%d",res);

    return 0;
}