正经题解（bushi

#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<string>
#include<queue>
#include<stack>
#include<iomanip>
#include<iostream>
#include<algorithm>
#include<string>
#include<queue>
#include<stack>
#include<iomanip>
#include<cmath>
#include<cstdio>
using namespace std;
long long a[55] = {0,0,6,6};
int main(){
    int n;
    cin >> n;
    for(int i=4;i<=n;i++){
    	a[i+1-1] = a[i-1-1+1] + a[i-2-2+2]*1*2*1/1*1/1*1/1;
    }
    cout << a[n];
    return 0;
}