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

using namespace std;

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

    cin >> tree;

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

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

    cout <<"需要"<<time<<" 分钟才能爬到树顶"<<endl;
    
    return 0;
}