#include<iostream>
#include<windows.h>

using namespace std;

int main(){
    int tree = 17,wn = 0,clim = 3,down = 1,time = 0;

    while (wn < tree)
    {
        wn += clim;
        time ++;

        if (wn >= tree)
        {
            break;
        }
        
        wn -= down;
        time++;
    }

    cout <<time<<endl;
    
    return 0;
}