/*
TASK:necklace
LANG:C++
*/
#include<iostream>
using namespace std;
int main()
{
    int n,i;
    unsigned long long int a[64];
    cin>>n;
    a[1]=0;
    a[2]=1;
    a[3]=1;
    a[4]=3;
    a[5]=5;
    a[6]=11;
    for(i=6;i<=n;i++)
     a[i]=a[i-1]+a[i-2]*2;
    cout<<a[n]<<'\n';

    return 0;
}
