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