#include<iostream>#include<cstdio>#include<cstdlib>#include<cstring>#include<algorithm>#include<vector>using namespace std;long long f[50];int main(){int n;while(scanf("%d",&n)&&n!=-1){f[0]=1,f[2]=3;for(int i=4;i<=n;i++)f[i]=f[i-2]*4-f[i-4];printf("%I64dn",f[n]);}}
