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