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#include<bits/stdc++.h>
#define ll long long
using namespace std;
ll a[1005];
int main(){
ll n;
cin >> n;
a[1] = 0;
a[2] = 6;
for(ll i = 3;i <= n;i++) a[i] = a[i-1] + a[i-2] * 2;
cout << a[n];
return 0;
}