链接：
https://codeforces.com/contest/1182/problem/A
题意：
You have a given integer n. Find the number of ways to fill all 3×n tiles with the shape described in the picture below. Upon filling, no empty spaces are allowed. Shapes cannot overlap.
This picture describes when n=4. The left one is the shape and the right one is 3×n tiles.
图片复制不了
思路：
给定形状只能再n为偶数的情况下完全覆盖，所以奇数不用考虑，同时，每两列为一组，一组有两种。
答案就是2^(n/2)。
代码:
#include <bits/stdc++.h>
using namespace std;
int main()
{
int n;
cin >> n;
int res = 1;
if (n%2 == 1)
cout << 0 << endl;
else
{
for (int i = 1;i <= n/2;i++)
res *= 2;
cout << res << endl;
}
return 0;
}