const int maxn = 40;

int dp[maxn][5];

void init() {
    dp[0][0] = dp[0][2] = 1;
    dp[0][1] = 0;
    dp[1][0] = dp[1][2] = 0;
    dp[1][1] = 1;
    for (int i = 2; i <= 30; i ++) {
        dp[i][0] = dp[i-2][0] + dp[i-1][1] + dp[i-2][2];
        dp[i][1] = dp[i-1][2];
        dp[i][2] = dp[i-1][1] + dp[i][0];
    }
}

int main() {
    int n;
    init();
    while (~scanf("%d", &n)) {
        if (n == -1) break;
        printf("%d\n", dp[n][0]);
    }
    return 0;
}

const int MAX=31;
int s[MAX];
int main()
{
    int i,n;
    s[0]=1;
    s[2]=3;
    for(i=4;i<MAX;i+=2)
    {
        s[i]=4*s[i-2]-s[i-4];
    }
    while(cin>>n,n>=0)
    {
        if(n&1)
            cout<<0<<endl;
        else
            cout<<s[n]<<endl;
    }
    return 0;
}