/*
TASK:necklace
LANG:C++
*/
#include<iostream>
using namespace std;
int main(){
    int n,a=1,b=1,i,br=0;
    cin>>n;
    for(i=1;i<n;i++){ a=a*2; b=b*2+1; }
    for(i=a;i<=b;i++) if(i%3==0) br++;
    cout<<br;        
    cout<<endl;
    return 0;
}
