#include<iostream>
#include<cstring>
#include<algorithm>
#include<set>
using namespace std;
int f[44],n;
signed main() {
int i;
f[3]=1,f[4]=3;
for(i=5;i<=30;i++){
f[i] = f[i-1]*2+ (1<<(i-4)) - f[i-4];
}
int x;
while(cin>>x,x){cout<<f[x]<<endl;}
}